Philosophy and the Sciences - Phil. Sci. Course

8/3/2019 Philosophy and the Sciences - Phil. Sci. Course

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eductive and Inductive Logic

hat is Reasoning?

xample: The first theorem Euclids Elementsprovides a good example of the kind of

asoning that people admire.

uppose we construct a triangle in the following way: 1. Draw a circle centered at point A.ark a point B on the circumference and draw a line from A to B. Draw a second circleentered at B that passed through A. Mark one of the points at which the circles intersect and draw lines from C to A and from C to B.

heorem : All the sides of the triangle ABC are of equal length.

roof: Let |AB| denote the length of the line segments AB, and so on.

Step 1: |AB| = |AC| because they are radii of the circle centered at A.

Step 2: |BA| = |BC| because they are radii of the circle centered at B.

Step 3: |AB| = |BA| because AB and BA denote the same line.

Step 4: |AC| = |BC| because they are each equal to the same thing (viz. |AB|

Step 5: Therefore, |AB| = |AC| = |BC| by steps 1 and 4.

efinition: An argumentis a list of statements, one of which is the conclusion and the reshich are the premises.

he conclusionstates the point being argued for and the premisesstate the reasons beingdvanced in support the conclusion. They may not be good reasons. There are good and ba

guments.

p: To identify arguments look for words that introduce conclusions, like "therefore",onsequently", "it follows that". These are called conclusion indicators. Also look for premidicatorslike "because" and "since".

emark: Each of the five steps in the proof to Euclids first theorem is an argument. Theonclusions in steps 1 to 4 are called intermediateconclusions, while the conclusion in stepthe mainconclusion.

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uestion: All arguments, or sequences of arguments, are examples of reasoning, but is evece of reasoning an argument? A perceptual judgment such as "I see a blue square", or t

onclusions of scientific experts reading in X-rays, or looking through a microscope, may bexamples of reasoning that are not arguments. They are derived from what Kuhn called tacnowledge, acquired through training and experience (e.g., knowing how to ride a bicycle).not easily articulated, and is not stated in any language.

he Difference between Good and Bad Arguments

logic, we assume that any reasoning is represented as an argument, and the evaluationn argument involves two questions:

1. Are the premises true?2. Supposing that the premises are true, what sort of support do they give the conclusio

nswers to question 2: Compare the following arguments.

1. All planets move on ellipses. Pluto is a planet. Therefore, Pluto moves on an ellipse.2. Mercury moves on an ellipse. Venus moves on an ellipse. Earth moves on an ellipse.

Mars moves on an ellipse. Jupiter moves on an ellipse. Saturn moves on an ellipse.Uranus moves on an ellipse. Neptune moves on an ellipse. Therefore, Pluto moves onan ellipse.

efinition: An argument is deductively validif and only if it is impossiblethat its conclusiolse while its premises are true.

xamples: Argument 1 is deductively valid, while argument 2 is not.

emark on terminology: The notion of deductively validity is such a central and importaoncept in philosophy, that is goes by several names. When an argument is deductively vale say that the conclusion follows fromthe premises, or the conclusion is deduced from, oferred from, or proved fromthe premises. Or we may say that the premises imply, or ent

provethe conclusion. We also talk of deductively valid arguments as being demonstrativl these different terms mean exactly the same thing, so the situation is far simpler than itppears.

hats possible? The sense of "impossible" needs clarification. Consider the example:

George is a human being. George is 100 years old. George has arthritis. Therefore, Georll not run a four-minute mile tomorrow.



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uppose that the premises are true. In logic, it ispossible that George will run a four-minutile tomorrow. It is not physicallypossible. But logicians have a far more liberal sense of w"possible" in mind in their definition of deductive validity. Argument 3 is not deductively

alid on their definition. So, argument 3 is invalid.

ey idea: In any deductively valid argument, there is a sense in which the conclusion isontainedin premises. Deductive reasoning serves the purpose ofextractinginformation fro

e premises. In a non-deductive argument, the conclusion goes beyond the premises.ferences in which the conclusion amplifiesthe premises is sometimes called ampliativeference.

herefore, whether an argument is deductively valid or not, depends on what the premisee.

Missing premises?: We can always add a premise to turn an invalid argument into a valgument. For example, if we add the premise "No 100-year-old human being with arthritis

ll run a four-minute mile tomorrow" to argument 3, then the new argument is deductivelyalid. (The original argument, of course, is still invalid).

efinition: An argument is inductively strongif and only if it is improbablethat its conclusfalse while its premises are true.

emember: This definition is the same as the definition of "deductively valid" except thatmpossible" is replaced by "improbable."

he degreeof strength of an inductive argument may be measured by the probability of thae conclusion is true giventhat all the premises are true.

he probability of the conclusion of a deductively valid argument given the premises is oneeductively valid arguments may be thought of as the limiting case of a strong inductiveguments. Ampliative arguments have an inductive strength less than one.

he probability of the conclusion given the premises can change from person to person, as

epends on the stock of relevant knowledge possessed by a given person at a given time.

ummary: In response to question 2, we may give answers like "the argument is valid", "tguments is inductively strong" or "the argument is inductively weak."

xercise: Discuss the following examples (all statements are understood to refer to the ye998):

4. There are multi-celled organisms living on Mars. Therefore, there is intelligent life



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Mars.

5. There are multi-celled organisms living on Mars. Therefore, there are single-celledorganisms living on Mars.

6. There are multi-celled organisms living in Lake Mendota. Therefore, there isintelligent life living in Lake Mendota.

7. There are multi-celled organisms living in Lake Mendota. Therefore, there are singcelled organisms living in Lake Mendota.

evertheless, in logic, it is assumed that the answer to question 1 is relevant to the evaluatan argument. But it is a question that needs to be asked in additionto question 2. So, if emises of an inductively strong argument are false, then logicians are forced to say that tgument is not a good one. It is confusing to say that an inductively strong argument is aeak argument, but this is how the terms are defined.

p: Defined terms must be used as defined. You cant use the term differently just becausou dont agree with the definition.

fferent Kinds of Ampliative Argument

efinition: Any argument that is not deductively valid, or deductively invalid, is called anmpliative argument. The term refers to the fact that the conclusion of such argument goes

eyond, or amplifies upon, the premises.

emark on terminology: Again the notion ofinvalid is so common and central, that it gy many names. Other terms commonly used are inductive and non-demonstrative. I prefempliativebecause it reminds us that the conclusion goes beyond the premises, and it doot have the bad reputation that sometimes goes along with the word induction.

ere are a variety of examples of ampliative arguments:

mple enumerative induction goes from a list of observations of the form "this A is a Bthe conclusion "All As are Bs". The example Hume made famous is like this:

8. Billiard ball 1 moves when struck. Billiard ball 2 moves when struck. Billiard ball 3moves when struck Billiard ball 100 moves when struck. Therefore, all billiard ballsmove when struck.

ome ampliative arguments go from general statements to general statements:



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9. All bodies freely falling near the surface of the Earth obey Galileos law. All planetsobey Keplers laws. Therefore, all material objects obey Newtons laws.

thers go from general statements to specific statements:

10. All emeralds previously found have been green. Therefore, the next emerald to bfound will be green.

onclusion : To understand empirical science we need to understand ampliative inference.

wo Kinds of Science? A Priori and Empirical?

1. A prioriscience, like Euclids geometry, is where the conclusions are deduced frompremises that appear to be self-evidently true.

2. In empirical science, like physics, conclusions are based on observational data.

This is similar to the distinction between pure mathematics and applied mathematicsThe distinction is not always sharp.

ver since Einstein rejected the use of Euclidean geometry in his new physics at the turn of

e 20th century, it seems that a priorisciences cannot tell us anything about the real worldhe focus of recent philosophy of science is on the empirical sciences.

A priori sciences contain the strongest form of reasoning, at the expense of telling us

less about the real world.

troduction to the Demarcation Problem

efinition: In philosophy of science, we refer to what we already know directly throughbservation as the empirical evidence(we are open-minded about the possibility that someese factsare mistaken). See Exercise 1.

l of empirical science uses ampliative arguments. Hume made the same point in a differenay. He pointed that in example 8, it is possible that the premises are true and the conclusfalse. No matter how many instances of a generalization we observe, it does not prove the generalization is true.

hat is the difference betw een science and pseudoscience?You often hear thatience is based on the factswhile pseudoscience is not. Or you say that religious belief is

ased on faith, whereas scientific belief is not. Unfortunately, both scientific and non-scientasoning go beyond the facts. So, can we tell them apart?



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rgument:

1. The demarcation between science and pseudoscience depends only the nature of thereasoning used.

2. Genuine science involves ampliative inference.3. Pseudoscience involves ampliative inference.

4. Therefore, there is no demarcation between science and pseudoscience.

he problem of demarcationis to say what is wrong with this argument. (Question: what e two things that can be wrong with an argument?)

eview of Central Definitions and Remarks on Terminology

efinition: An argument is deductively validif and only if it is impossiblethat its conclusiolse while its premises are true.

emark: The notion of deductively validity is such a central and important concept inhilosophy, that is goes by several names. When an argument is deductively valid, we say te conclusion follows fromthe premises, or the conclusion is deduced from, or inferred froproved fromthe premises. Or we may say that the premises imply, or entail, or proveth

onclusion. We also talk of deductively valid arguments as being demonstrative. All thesefferent terms mean exactly the same thing, so the situation is far simpler than it appears.

efinition: Any argument that is not deductively valid, or deductively invalid, is an ampliargument. The term refers to the fact that the conclusion of such argument goes beyond, omplifies upon, the premises.

emark: Again the notion ofinvalid is so common and central, that it goes by many namether terms commonly used are inductive and non-demonstrative. I prefer ampliativeecause it reminds us that the conclusion goes beyond the premises, and it does not havee bad reputation that sometimes goes along with the word induction.



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emarcation: Popper, Kuhn and Lakatos

ast modified on Friday, September 18, 1998. Malcolm R. Forster, 1998

he Problem

he difference between science and non-science has practical ramifications for society:

Parapsychology includes the study of such alleged phenomena as telepathy,clairvoyance, and precognition. In 1969 the American Association for the Advancemeof Science (AAAS) admitted the Parapsychology association as an Affiliate member.Should they have done that?

In Arkansas, U. S. A., there were attempts to have the biblical story of creation taughin schools alongside evolutionary theory (after earlier attempts to ban evolutionary

theory failed). They argued that creationism is a just as much a science, and therefodeserves equal time.

The Merriam-Webster's CollegiateDictionarydefines creation sciencen(1979):creationism; also: scientific evidence or arguments put forth in support of creationismShould an authoritative dictionary presuppose that creationism is a science?

Freudian psychology has a poor reputation in scientific circles. Is it a pseudoscience? Immanuel Velikovsky and Erich van Daniken wrote best sellers Worlds in Collisionan

Chariots of the Gods, which angered many scientists. Are these examples ofpseudoscience.

Thor Heyerdahl launched the Kon-Tiki expedition to support his theory that thepolynesians migrated from South America. Was he a pseudoscientist?

Gould wrote a book called The Mismeasure of Manabout the IQ debate, andphrenology, which purported to predict the criminal nature of people from their skull

shape and other characteristics. IQ testing has been used to screen children from entering high school, or college, in

many countries for many years. Does it predict future academic performance reliablythere really such a thing as intelligence?

Chemistry grew out of alchemy. Ones a science and the other is not. Whats the

difference? The label 'science' carries a high degree of authority, and people need to understand

when the label, and the authority, are deserved. Is there any clear difference betweean unscientific study and a scientific one?

More generally, an understanding of what science is carries us a step closer to tellingthe difference between good and bad science, and the limits of good science. If weunderstand how science works, we can be better and more informed use of scientificexpertise.

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we wanted to know which subjects were generally acceptedas science, we would probabnd a fairly sharp and clear division between two categories. But we are interested in morean that! We want to understand the general characteristics of science that are different fr

seudoscience. That is actually surprisingly difficult and controversial.

xercise: Critically evaluate the following characterization of science (from the Encyclopedritannica): any system of knowledge that is concerned with the physical world and its

henomena and that entails unbiased observations and systematic experimentation. Ineneral, a science involves a pursuit of knowledge covering general truths or the operationfundamental laws.

xamples of Science and Pseudoscience

he key to understanding Popper's demarcation criterion is to compare two examples. The

st, Popper thinks is typical of science, while the second is typical of pseudoscience.

xample (a): Einstein's prediction of the bending of star light. For over 200 years prior tonstein, Newtonian physics had enjoyed a period of unprecedented success in science. Maientists thought that Newton's theory was the end of science, and many philosophers not

nly believed that Newton's theory was true, they thought that it was necessarilytrue. Theyought to explain why Newton's theory hadto be true. All that began to change with Planck900 introduction of the idea that energy comes in small discrete packages (the quantumypothesis) and Einstein's discovery of the special theory of relativity in 1905. Einstein'special theory of relativity was a way of reconciling some inconsistencies between the waveeory of light and Newtonian mechanics. Instead of modifying the wave theory, he modifie

ome of the fundamental assumptions used in Newtonian physics (like the assumption thatmultaneity did not depend on a frame of reference, and that the mass does not depend os velocity). However, Einstein's special theory of relativity said nothing about gravity.nstein's generaltheory of relativity was his theory of gravitation, which he had published 916. Many scientists were impressed by the aesthetic beauty of Einstein's principles, but itas also important that it be tested by observation. For most everyday phenomena, in whicelocities are far smaller than the speed of light, there is no detectable difference betweennstein's prediction and Newton's prediction. What we needed was a crucial experimentinhich Einstein and Newton made different predictions. In 1916, there were successful testsnstein's special theory. But crucial tests of the general theory were harder to come by. Onch case was provided by the bending of starlight by the gravity of the sun. The period fro

900 to at least 1916 was a period ofrevolutionin physics, and Eddington's confirmation ofnstein's prediction in 1919 helped to complete the change in physics.

The idea that light should be deflected by passing close to a massive body had beenggested by the British astronomer and geologist John Michell in the 18th century. Howevnstein's general relativity theory predicted twice as much deflection as Newtonian physics

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uick confirmation of Einstein's result came from measuring the direction of a star close to un during an expedition led by the British astronomer Sir Arthur Stanley Eddingtonto obsee solar eclipse of 1919. Optical determinations of the change of direction of a star arebject to many systematic errors, and far better confirmation of Einstein's general relativiteory has been obtained from measurements of a closely related effect--namely, the increthe time taken by electromagnetic radiation along a path close to a massive

ody." (Encyclopedia Britannica)

The theories involved here were Einstein's general theory of relativity and the Newtonianarticle theory of light, which predicted only half the relativistic effect. The conclusion of thxceedingly difficult measurement--that Einstein's theory was followed within the experimemits of error, which amounted to +/-30 percent--was the signal for worldwide feting ofnstein. If his theory had not appealed aesthetically to those able to appreciate it and if thad been any passionate adherents to the Newtonian view, the scope for error could well heen made the excuse for a long drawn-out struggle, especially since several repetitions atbsequent eclipses did little to improve the accuracy. In this case, then, the desire to belie

as easily satisfied. It is gratifying to note that recent advances in radio astronomy haveowed much greater accuracy to be achieved, and Einstein's prediction is now verified with

bout 1 percent." (Encyclopedia Britannica)

According to this theory the deflection, which causes the image of a star to appear slightlyo far from the Sun's image, amounts to 1.75 seconds of arc at the limb of the Sun and

ecreases in proportion to the apparent distance from the centre of the solar disk of the stahose light is deflected. This is twice the amount given by the older Newtonian dynamics ifht is assumed to have inertial properties. If light does not have such properties, as is

enerally accepted now, the Newtonian deflection is zero." (Encyclopedia Britannica)

econstruction of the example: Philosophers need a generalcharacterization of thexample: Let Ebe a statement of the prediction made by Einstein's theory. Estates therection that the starlight will be observed at the time at which the star was to be observey Eddington. Let Tbe a statement of the general principled in Einstein's general theory oflativity. LetAbe the conjunction of all auxiliary statements used to derive, or deduce, EfThat is to say, the argument with TandAas premises, and Eas the conclusion, is

eductively valid. Symbolically, we may write this as:

T&AE.

will include assumptions like "the sun is spherical ball of mass M", "there are no other bodose by to add to the sun's gravitational field," "If the sun were not present, then the starould be seen in the direction such-and-such," "the effect of stellar aberration on the direclight is such-and-such," and so on.

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xample (b): Adler's 'individual psychology'. Compare the following two (hypothetical)xplanations of human behavior. (1) E1: A man pushes a child into the water with the

tention of drowning it. (2) E2: A man sacrifices his life in an attempt to save the child.

opper claims that Adler's 'individual psychology' can explain both of these behaviors withqual ease. Let Tbe Adler's theory, letAbe the auxiliary assumption that the man sufferedelings of inferiority (producing the need to prove to himself that he dared to commit some

ime). Then T&A1E1. LetA2 be the auxiliary assumption that the man suffered feelinginferiority (producing the need to prove to himself that he dared to rescue the child). NoA2E2.

efinition: Let us say that a theory Tpredictsan event Eif and only if there are auxiliaryssumptions that have either been used successfully in other predictions, or are the simplesnd most obvious assumptions that one would make in the situation, and that T&AE. Iere exists auxiliary assumptions such that T&AE, whereAis some ad hocassumptio

at is introduced in light of the evidence Eitself, then theory Tmerely accommodatesE.

example (a), Einstein's theory predicts the observational evidence, while in example (b),eory is merely accommodates the evidence.

opper describes the difference by claiming that Einstein's theory is falsifiable, whereas Adl

eory is not.

emark: Popper also claims that the problem with Adler's theory is that it is too easily

erified: "the world was full ofverificationsof the theory." Adler may have seen it like that,as he right? My feeling is that mere accommodations do not count as verifications at all.ence, I think that a verificationist could account for the difference between these twoxamplesas well as, if not better than, a falsificationist.

scussion Question: How does our previous distinction between ampliative inference aneductive inference enter into these examples, if at all. Popperians tend to think that there o need for ampliative inference in science at all. Why might they think that? Are they right

opper's Path to his Demarcation Criteria

Curd and Cover, pages 1-10) To understand a philosophical theory, like Popper's demarcatiterion, it is useful to see why simpler alternative proposals do not work.

roposal 1: Science is distinguished by its empirical method. That is, science is distinguishom pseudoscience by its use of observational data in making predictions.



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bjection:Astrologyappeals to observation, but is not a science.

roposal 2: Scientific theories, like Einstein's, are more precise in their predictions thatdler's psychology, or astrology.

bjection: While it is true that pseudosciences do often protect themselves from refutatioy making vague or ambiguous predictions, that is not always the case. The 'predictions' ofxample (b) are precise enough for the purpose, and Einstein's prediction was not exactitad to allow for many errors of observation.

roposal 3: Science is explanatory, whereas pseudoscience is not.

bjection: If you buy into the auxiliary assumptions in Adler's psychology, then the theoryxplainsthe phenomena perfectly well. It is true we have little reason to believe that thexplanation is correct, but that is a different issue.

roposal 4: Science is distinguished from pseudoscience by its verifications, or confirmatio

bjection: Popper's objection is that "The world was full of verifications of those theories.ave remarked that that does not ring true in examples (a) and (b). Nevertheless, thereems to be some force behind Popper's point in other examples. For example, Einstein cou

ave pointed to all the verifications of Newton's theory for low velocities and claim these aserifications for his own theory. Yet he did not. Why not? Because, says Popper, these wereot riskypredictions. They were not potential falsifiers of Einstein's theory.

oppers Proposal: Every good scientific theory is a prohibition: it forbids certain things appen. The criterion of the scientific status of a theory is its falsifiability, or refutability, orstability.

ote: Popper also anticipates a major objection to his criterion: namely, that anyscientificeory can be protected from refutation by introducing ad hocauxiliary assumptions. His rethat the very use ofad hocassumptions, in reducing the falsifiability of theory, alsominishes its scientific status. The problem with Poppers reply is that it is not always, if ev

ear in advance that ad hocauxiliary assumptions are needed to save the theory. This isssentially Kuhns point.

ypothetico-Deductivism

the first set of lecture notes, I introduced the demarcation problem as a problem about t

fference between good and bad kinds of ampliative inference. Popper rejects thisrmulation of the problem. He thinks it is wrong to think of theories as being inferred fromduced from, the observational facts. Rather, the invention of theories is a question of

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sychology, which has nothing to do with the status of the theory as scientific. There are noientific or unscientific ways of inventing theories. They can come in a dream or they can b

onstructed from the datait does not matter. Rather, the essence of science is about howedictions are deduced from the theories. This way of viewing science is known as

ypothetico-deductivism. The difference between science and pseudoscience rests solely on

e 'deductive' part of the process.

uhns Characterization of Science

homas Kuhn makes the following points against Popper (Curd and Cover, pages 11-19):

The kind of examples Popper considers, like the 1919 test of Einsteins theory ofgravitation, is an example of extraordinary science, or revolutionary science. These arelatively rare in science.

In non-revolutionary science, or normalscience, the aim of research is to connect theexperimental data to the background theory, by inventing the appropriate auxiliaryassumptions. If a scientist fails, then scientists lack of ingenuity is blamed, not thetheory.

It is for normal, not extraordinary, science that scientists are trained, and... "If a demarcation criterion exists..., it may lie in that part of science which Sir Karl

ignores."

uestion: Kuhn concedes that "There is one sort of 'statement' or 'hypothesis' that scientio repeatedly subject to systematic test. I have in mind statements of an individuals guessbout the proper way to connect his own research problem with the corpus of acceptedientific knowledge." Thus, thinks (a) a demarcation criterion should refer to normal scienc

nd (b) falsifiability does play a role in normal science. So, why doesnt he apply a falsifiabiiterion to normal science, and say that an alleged science is genuinely scientific if and onls solutions to puzzles are falsifiable? As Kuhn says, this is not what Popper has in mind. Buoes the new criterion work?

entral Concepts in Kuhns Account of Revolutionary Change in Science: Kuhn deat theories change by falsification in science, but he does not deny that theories are

ometimes replaced(revised). What is his own account oftheory replacement

? Here is verief summary of his positive account:

1. The process by which one paradigm is replaced by another is called revolutionaryscience.

2. An anomalyis a violation of "the paradigm-induced expectations that govern normalscience" (Kuhn, The Structure of Scientific Revolutions, 1970, p.52).

3. Acrisisin normal science occurs when puzzle-solving breaks down, either because nosolutions are found, or because the discrepancy corrected in one place shows up in



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another.4. A paradigm is overthrown only if the paradigm is in crisis and there is a second

paradigm that shows equal or greater puzzle-solving potential.

uhns Demarcation Criterion: All of genuine science has a puzzle-solving tradition, whseudosciences do not.

bjection: Until Kuhn says what a puzzle-solving tradition is, his criterion is rather vague.hy wouldnt a research tradition that sought worked backwards from the fact to the auxili

ypotheses count as puzzle-solving. It seems that Kuhn needs to add something likelsifiability.

uhn on Astrology:

1. Kuhn agrees that astrology is pseudoscience, but makes the point that it was notobvious that it was pseudoscience in the century it was practiced most. That is becauits auxiliary assumptions, based on the configuration of the planets at the time of birwere subject to genuine doubt. Not everyone was sure of their exact date of birth inany case. The problem is that similar arguments explaining away failed predictions aregularly used today in medicine or meteorology.

2. Astrologyhas no science to practice because practitioners had rules to apply, but no

puzzles to solve. Most difficulties "were beyond the astrologers knowledge, control, aresponsibility." In astronomy, however, if a prediction failed, a scientist "could hope tset the situation right." There was a puzzle-solving tradition.

nal argument:

For a long period of time, there was a sense in which Ptolemaic astronomy wasunfalsifiable by the means available (naked-eye observations). But that did not stop ifrom being science at the time. Moreover, when it was finally falsified (by Galileosobservation of the phases of Venus, the moons of Jupiter, and Brahes observations comets), it had already been rejected.

ecessary and Sufficient Conditions

ecessary condition: E.g., being enrolled in this course is a necessary condition for youetting an A for the course. That is, you will not get an A if you are not registered. Orquivalently, if you do get an A, then you are registered. In general: A necessary condition n event or state of affairs Xis one that has to hold for Xto be true. A necessary condition ontrasted with a sufficient condition.

ufficient condition: E.g., getting an A in this course is a sufficient condition for passing t

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ourse. That is, it you get an A then you will pass. In general: A sufficient condition for anvent, or state of affairs Xis one that enough to makes Xtrue.

ecessary and sufficient condition: A condition is necessary and sufficient for aatement, or event, Xif and only if it is necessary for Xand sufficient for X. It is often

xpressed by the phrase if and only if or the abbreviation iff. E.g., a necessary and sufficiondition for passing this course is to receive a passing grade while being registered for the

ourse.

opper says that the falsifiability is a necessary and sufficient condition for genuine science

Falsifiability is not a sufficient condition because astrology is falsifiable but not ascience. In the 1960s, Michael Gauquelin examined the careers and times of birth of25,000 Frenchmen, and found no significant correlation between careers and either ssign, moon sign, or ascendant sign (see the Thagard reading). Gauquelin found somestatistically significant correlations between certain occupations and the positions ofcertain planets at the time of their birth, but we can expect 1 in 20 random associatiowill be statistically significant by chance alone. Also, studies of twin do not show thecorrelation one would expect. These results cannot be explained away by supposingthat almost all assumptions in every case were false. Therefore, such a study falsifiesastrology in a sense that Popper would accept, and these studies were always possibwhich proves that astrology was always falsifiable.

Falsifiability is not necessary for science. The example of Ptolemaic astronomy showsthis, because prior to the invention of telescope it was not falsifiable but it was still ascience.

ounterexamples: In order to show that a condition is not a sufficient condition for X, wenly need an example in which the condition holds, but X does not. In order to show that aondition is not a necessary condition for X, we only need an example in which X holds but ondition does not. In each case, the examples are called counterexamples. Astrology is aounterexample for the sufficiency of falsifiability for science, and Ptolemaic astronomy isounterexample to its necessity.

ere are some other arguments that make use of counterexamples.

Astrology is not a science because it has mystical origins. Counterexample: Chemishad its origins in alchemy and medicine had occult beginnings.

Astrology is not a science because people believe astrology for irrational reasons.Counterexample: Many people believe in Einstein's theories for irrational reasons.

Astrology is not a science because it assumes that gravitational influences of the planinfluence us, but they are too weak to do that. Counterexamples: The lack of aphysical foundation did not stop geologists from believing in continental drift, and we



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have plenty of evidence to prove that smoking causes lung cancer with knowing thedetails of the carcinogenesis.



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akatos's Methodology of Scientific Research Programs

ast modified on Thursday, September 24, 1998, by Malcolm R. Forster

oints of Disagreement between Lakatos and Kuhn

1. Subjective or objective?Kuhns demarcation criterion appears to be subjective--itdepends on what scientists do and what they believe (their psychology). In contrast,Lakatos insists that "a statement may be pseudoscientific even if it is eminentlyplausible and everyone believes in it." Belief that earth is flat may count as an examof that. And "it may be scientifically valuable even if it is unbelievable and nobodybelieves in it." Copernicus's theory that the sun moves like that, and very few believein evolution when Darwin introduced his theory.

2. Sociology or logic?Another point of disagreement between Kuhn and Lakatos is

whether a demarcation criterion should be talking about which statementsare scientor pseudoscientific, or whether it should be saying which communityis scientific orunscientific. Lakatos, as a neo-Popperian, was raised in the tradition in which logicwthe main tool in philosophy of science, whereas Kuhn is more interested in the sociolof science.

3. Religion or Science?Kuhn compares science to religion, but Lakatos rejects thiscomparison.

ain Point of Agreement between Lakatos and Kuhn

ny good science can be practicedin a pseudoscientific way. The demarcation betweenience and pseudoscience refers to its method and not just what the theory says (its conte

For example, some evolutionists may be tempted to fill in auxiliary assumptions in anhocway by working backwards from what is to be explained. For example, if see fromthe fossil record that horses teeth become elongated, we may be tempted into usingevolutionary theory to infer that there was some change in the environment that madshorter teeth less fit, and then explain the change by appealing to the law of natural

selection that "only the fittest survive." It would be equally easy for Newtonian mechanics to be practiced in a pseudoscienti

way. After all, Newtons law of inertia says that a body continues in a straight line wituniform velocity until acted on by a force, and then defines a force as anything thatdiverts a body from uniform motion in a straight line.

akatos on Poppers Demarcation Criterion



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1. Lakatos argues that falsifiable already refers to how science is practiced. He interprePopper as demanding that scientists "specify in advance a crucial experiment (orobservation) which can falsify it, and it is pseudoscientific if one refuses to specify sua potential falsifier. If so, Popper does not demarcate scientific statements forpseudoscientific ones, but rather scientific method from non-scientific method."

2. While Poppers criterion does focus on practice, it is still wrong because it "ignores thremarkable tenacity of theories." Scientists will either invent some rescue hypothesis

(accommodate the theory) or ignore the problem and direct their attention to otherproblems. For example, some problems may be too hard (nobody rejected Newtoniamechanics because it couldnt predict all the properties of turbulent fluid flow, or thechaotic motion of a physical pendulum).

Puzzle about Prediction

arlier, we saw that Popper's two examples, Adler's theory at one extreme, and Einstein'seory at the other, illustrated a difference between accommodation and prediction. Adler's

eory merely accommodated the facts because it worked backwards from the evidence Ete auxiliary assumptionAneeded so that the theory Tentailed E(T&AE). At the othe

xtreme, if intellectual honesty requires that a scientist specify a potential falsifier indvance, then they must specifyAin advance. That is a sufficientcondition for the theory take a prediction. But is it necessary?

akatoss Picture of Science

he typical unit of science is not an isolated hypothesis, but rather a researchprogramme,

onsisting in a hard core(theory), protective belt(auxiliary assumptions) and a heuristic.

akatos quote: Aheuristicis a "powerful problem solving machinery, which with the help ophisticated mathematical techniques, digests anomalies and even turns them into positivevidence. For instance, if a planet does not move exactly as it should, the Newtonian scienthecks his conjectures concerning atmospheric refraction, concerning propagation of light inagnetic storms, and hundreds of other conjectures that are all part of the programme. Heay even invent a hitherto unknown planet and calculate its position, mass and velocity inder to explain the anomaly." (Lakatos, 1977, p. 5)

In Kuhn's terminology: Heuristics are hints about how to solve normal science puzzle

In my terms: A heuristic is a hint about how to change the auxiliary assumptions so tthe theory better fits the facts.

he negative heuristicforbids scientists to question or criticize the hard core of a researchogramme. "The positive heuristicconsists of a partially articulated set of suggestions or h



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n how to change, develop the 'refutable variants' of the research programme, how to modophisticate, the 'refutable' protective belt." (Lakatos, 1970, p.135).

xample: Le Verrier andAdams were faced with the following problem in Newton's theory

anetary motion. There were discrepancies (unpredicted wobbles) in the motion of theutermost planet known at the time (Uranus). They postulated that these might be caused hitherto unknown planet. Based on that conjecture they recalculated the solutions to

ewton's equations, and fit the solutions to the known data for Uranus. That fit even predice position of the postulated planet, whereupon Neptune was seen for the first time oncelescopes were pointed in that direction (actually, it was later discovered that it had beenen before, but mistaken for a comet).

In this example, the positive heuristic used was something like this: "If there is ananomaly in Newton's theory on the assumption that there are nplanets, then tryassuming that there are n+1 planets."

he Role of Background Evidence

e have identified auxiliary assumptions with Lakatos's protective belt. That is, we aressuming that auxiliary assumptions are always provisional in some sense. However, we muow decide whether to count statements of background evidence, prior observations, andata, as auxiliary assumptions. They are auxiliary in the sense that they are needed in ordeake predictions. In the Le Verrier-Adams example it would be impossible to predict theosition of the postulated planet without making use of the observed positions of Uranus, ae other planets. Let use refer to this background databy the letter D('D' for data). We noplace the previous pattern of inference (T&AE) by the pattern:

T&A&DE.

e still refer toAas the auxiliary assumption, but with the explicit understanding that itxcludesthe background observational evidence or data D.

odels

may be useful at this point to introduce the concept of a model. Amodelis theoretical

atement, (often in the form of an equation) usually deduced from a theory with the aid a

uxiliary assumptions. That is, a model Mis equal to a theory Tcombined with an auxiliary

ssumptionA(which will be long list of assumptions in most cases). That is, M= T&A.

xample: In the LeVerrier-Adams example, there was first a Newtonian model of planetaryotion that assumed that there are only 7 planets. There were discrepancies between the

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edictions of this model and the observed motions of Uranus. Therefore, the model wasplaced by one that assumed the existence of 8 planets. Not only did that accommodate th

nomalous motion of Uranus, but it predicted position of the eighth planet, whereuponeptune was discovered.

emarks:

1. A model Mis falsified when M&DEbecause Dis not blamed for the failedprediction. Therefore, models are falsifiable, or refutable, even though theories are n

2. The notion of a 'model' corresponds to Lakatos's notion of a 'refutable variant of atheory'. If a Lakatosian heuristic defines an ordered list of auxiliary assumptions,A0,

A2,A3, ... then it also defines an ordered list of models M0, M1, M2, M3, ...

3. This use of the term 'model' differs from two other uses that are common in thephilosophy of science. (a) A 'model' as in a model airplane. Such models do appear inscience, such as in the 'model of the DNA molecule' Watson and Crick used, which w

made of wooden balls joined with sticks. (b) 'Model' in the sense used bymathematicians in model theory. There it has a rather technical meaning, whichcorresponds roughly to what logicians call an interpretation of a language(anassignment of objects to names, set of objects to properties, a set of object pairs torelations, and so on).

4. Scientists use the term 'model' all the time, and it very rarely fits sense (a) andabsolutely never fits sense (b). Our use of the term best fits the standard scientificusage.

olution to the Puzzle about Prediction

a heuristics exists, then a scientist has an ordered list of suggested models M0, M1, M2,

3, ... Now the theory Tis no longer falsifiable in Popper's methodological sense, for if a

ientist tries makes the prediction E0 from model M0 and E0 proves to be false, then the

ientist does not blame T, but instead moves to M1, because it is next on the ordered list,

nd so on. Scientists now predict E1 because M1 &BE1. And so on. There is no falsifiab

the theory, but it can still make predictions. Thus, the idea of a heuristic may save thestinction between accommodation and prediction, and thereby providing a weaker sufficie

ondition for prediction.

Note that the research program makes a different set of predictions at different timeThis allows Lakatos to introduce the idea ofnovelpredictions--new predictions not mbefore.

hen Should One Model Supercede Another?



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akatos does not believe that falsification is important in science, but like Kuhn, he doescognize that theories, or paradigms, are superceded in science. He objects to Kuhn's

escription of this process, of scientific revolutions, as being a like a religious conversion, oocial revolution. Lakatos things that the process is more objective. Here is his view.

hesis: A model Msupercedes a model Mif and only if (1) Mhas excess empirical conte

ver T: that is, it predicts novelfacts, that is, facts improbable in light of, or even forbiddey M; (2) Mexplains the previous success ofM, that is, all the unrefuted content ofMisontained (within the limits of observational error) in the content ofM; and (3) some exceontent ofMis corroborated. (see Lakatos, 1970, p. 116; the phrase "should supercede" iy paraphrase, and I have replaced 'theory' by 'model'.)

This is Lakatos's account of normal science.

akatos introduces some new terminology to help formulate his theory of science.

1. Aproblemshiftis a series of models ...M1, M2, ... such that (i) each can explain the

empirical success of its predecessor, and (ii) each can explain at least some of theemprical failure of it predecessor as well. In other words, a Lakatosian problemshiftoccurs whenever a Kuhnian solution to a normal science puzzle is found, since to be solution is must remove the anomaly with creating new one. Note that a problemshifdoes not have to make novel predictions.

2. Atheoretically progressiveproblemshift is a problemshift that predicts some novel fa

3. A problemshift is empirically progressiveif it is theoretically progressive and some of novel predictions have been corroborated.

ote: In Lakatos's original writings, Lakatos uses the word 'theory' instead of 'model', butnly because he fails to make the distinction. I think that he models in mind.

efinition: A problemshift is progressiveif it is theoretically and empirically progressive.therwise the problemshift is degenerating. The idea of a degenerating problemshiftorresponds to Kuhn's notion of crisis.

xample 1: The LeVerrier-Adams discovery of Neptune is a great example of a problemshat was progressive, because (1) it led to novel predictions (the position of Neptune), whic) were then corroborated.

xample 2: Ptolemaic astronomy was degenerating not because it failed to be theoreticallogressive (Ptolemaic astronomers had the option of adding more epicycles) but because ias not empirically progressive. That is, adding an epicycle would lead to novel predictions



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ut they were not corroborated (confirmed).

akatos on Revolutions

hat is Lakatos's theory about when one theoryshould supercede another? In fact, Lakatooes not provide such a criterion. Not even when one research program is degenerating annother is progressive does Lakatos say that scientists do or should only work on the

ogressive one, because like the stock-market, they may change their status over time.

The methodology of scientific research programmes does not offer instant rationality

is not irrational for a scientist to work on a young research programme if she thinks it shootential. Nor is it irrational for a scientist to stick with an old programme in the hope ofaking it progressive. Thus, Lakatos appears to agree with Kuhn that theory change is ather fuzzy phenomenon. But he does insist that it depends on the assessment ofobjectivcts--the futureprogressiveness or degeneration of research programs. The decision ofientists, however, must rely of their subjective predictions of the future course of sciencenlike Kuhn, Lakatos does notthink that the uncertainty makes these decisions irrational.

xample 3: Prout's program. Prout, in 1815, claimed that the atomic weights of all pureements were whole numbers. He knew that the experimental results known at the time dot confirm his theory, but he thought that this arose because chemical substances as theyaturally occurred were impure. Thus, there ensued a program of research whereby chemicbstances were purified by chemical means. This program led from one failure to the next

he program at this stage was degenerating. However, Rutherford's school explained thisilure by the fact that different elements can be chemically identical(as explained by theeriodic table). They proposed that the substances should be purified by physical meansowerful centrifuges), whereupon the program made a progressive shift. Lakatos (1970,

p.138-140) uses this as an example of why it would be wrong to advise scientists to instanbandon a degenerating research program.

uestion: We have talked about Lakatos's view of normal science and revolutionary sciencowever, this is separate from the demarcation issue. Popper thinks that the essence ofience lies in the nature of revolutions, but Kuhn thinks that the essence of science lies in

ature of non-revolutionary science. Where does Lakatos stand on this issue?

akatos's Demarcation Criterion

akatos is not explicit about his demarcation criterion in the passage we read, but he is expbout in his 1970 article: "We 'accept' problemshifts as 'scientific' only if they are at leasteoretically progressive; if they are not, we 'reject' them as 'pseudoscientific.'" (1970, p. 1



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esumably, therefore, a research program is scientificif and only if it is at least theoreticalogressive. Note that it is possible for a research program to be scientific at one time, but another. It is even that a program practiced by one group is scientific, while the practice

nother group is pseudoscientific. This is how Lakatos is agreeing with Kuhn's point that evgood theory can always be practicedin a pseudoscientific was. Thus, Adler's theory (abouferiority complexes) might potentially be a good theory, but the fact is that it was beingracticedin a pseudoscientific way (if Popper's account is correct).

Lakatos is agreeing with Kuhn, against Popper, that the essence of science lies in thenature ofnormalscience.

xample 4: Astrology. Astrology has no theoretically progressive problemshifts, and therefo empirically progressive problemshifts. That is, it made no novelpredictions, despite thatct that it made predictions. Therefore, astrology was not a science.

xample 5: Prout's program. While Prout's program was degenerating, it was still

eoretically progressive, and hence scientific.

xample 6: Jeane Dixon was a self-proclaimed psychic who predicted that JFK's

ssassination. She made over 200 predictions each year (most of them wrong of course). Der method count as scientific? It would be by Popper's criterion, but not by Kuhn's orakatos's demarcation criteria. Like astrology, there was no Kuhnian puzzle solving, and noeoretically progressive problemshifts.

usgrave's Criticisms of Lakatos

an article called "Method or Madness" (in Cohen, R. S., Feyerabend, P. K.. and Wartofsky. W. (eds) Essays in Memory of Irme Lakatos, Dordrecht, Holland, D. Reidel), Alan Musgra976) raises some interesting objections to Lakatos's theory of science, which I have

xpanded upon in places.

1. Is the negative heuristic needed? Before 1850, Newtonian seldom treated Newtolaw of gravitation as part of the hard core. Therefore, scientists did not follow Lakato

methodology and render Newton's laws unfalsifiable by fiat. And why should scientisthave to specify in advancenot to modify or renounce them in the face of difficulties.Surely, it is enough that it is harder to produce theoretically problemshifts by changincentral assumptions because it is then harder to explain all the successes of thesuperceded model. But there is no reason to rule it out in advance.

2. Are positive heuristics alw ays specified in advance? Where was the positiveheuristic in the example of Prout's program? No-one tried physical separation ofchemical substances as soon as the chemical methods failed. They kept trying toimprove the chemical methods. It was only after the discovery of chemical similaritie

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that the hint or suggestion appeared.3. Why not compare one research program against another? Musgrave thinks th

Lakatos is overcautious in not recommending any rule for choice between competingresearch programs. Why not say, that on the whole, the scientific community shoulddevote more resources to progressive as opposed to degenerating research program



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volutionary Theory

ast modified on Friday, October 02, 1998, by Malcolm R. Forsterxtracted in part from "Philosophy of Biology" by James G. Lennox)

act versus theory:

act of evolution = the fact that evolution has occurred.

heory of evolution = an explanation about how and why evolution has occurred.

ote: Darwin did help establish the factof evolution. However, the fact of evolution wasready accepted by some prominent biologists prior to Darwin, so this is not his most

mportant claim to fame.

It is possible to accept the fact of evolution, but to seriously disagree with (or evenmisunderstand) Darwins theory of how the fact of evolution come about.

arwins theory of evolution is roughly as follows:

1. The struggle for survival: Biological organisms have more offspring than can posssurvive.

2. Inheritabil ity: Biological organisms inheritsome of their traits from their ancestorsand pass them onto their descendents.

3. Variation: The inheritable traits of biological organisms vary, even within the samespecies.

4. Differential fitness: Some inheritable traits will be more advantageous than othersthe struggle for survival.

herefore, there has been and will continue to be, on average, a (natural) selection of thoganisms that have advantageous traits that will lead to the evolution of species.

his is what Lakatos would call the hard core of Darwins research program.

he radical nature of Darw ins theory

he fact of evolution is radical enough, especially in light of the extremely recent arrival ofomo sapiens. It questions the primacy of our place of the universe. However, the Darwinseory is even more radical than that. Darwin delayed publication of his theory for many

ears; in fact he only published when he discovered that Wallace was about to publish the



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me theory. The probable reason for his delay was a fear of the controversy his theorywoovoke.

1. Darwins theory undermines one of best theological arguments for theexistence of God: If you come across a watch, and observed its intricate design, thit is reasonable to infer the existence of a watchmaker. If you come across a biologicorganism that has an even more intricate design, then it is reasonable to infer the

existence of a Creator. This is called the argument from design. Evolutionary theoprovides an alternative explanation. Moreover, the imperfection of many designs isevidence for evolution and against design.

2. Darwins theory does not imply that evolution is progressive. Evolution has npredetermined direction. The direction of evolutionary change depends on the localenvironment at the time. There is no progression from inferior to superior organismsimplied by the theory. In fact, immoral traits like ruthlessness and violence are oftenrewarded in evolution. In particular, there is no implication that homo sapiensissuperior to other species. There is no final causedirecting evolutionary change.

Evolution is not teleologicalor goal directed.3. Darwins theory supports a materialistic world view (nothing to do with

materialism in the consumer sense). The view that humans have souls, while animalsnot, finds no place in Darwins theory. It supports the view that the only things in theuniverse are material things.

he protective belt: Darwins theory predicts (or postdicts) that evolution has occurred.owever, the theory, by itself, does not say which traits are inheritable, nor how they vary,e way in which resources are limited, or how the different traits aid in survival, or how all

ese factors change over time.

modelof a particular episode or instance of evolutionary change will add specific details te hard core assumptions, concerning:

a. the range of inheritable traits in a biological population(s).b. the environment, and how it changes over time.c. the relative benefit that these traits confer to the members of the populations

possessing them in the various environments (fitness values).

ccommodation versus prediction : Some of these details may be introduced asarameters (e.g., fitness parameters), which are inferred backwards from facts to bexplained. But if all of these details are inferred from the facts to be explained, then theeory is merely accommodatingthe facts, and there are no predictions (or postdictions). Inat case, evolutionary theory would be pseudoscientific according to Lakatoss demarcationiterion.



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he positive heuristic, if it exists, should suggest how these details should be filled inould the most plausible assumption fail to accommodate the observational facts.

efinition:Ahomologyis a similarity between or amongst different species that is the restheir common ancestry. There are at least 3 kinds of homologies: (a) Structural homologch as the similarity between the bone structure in a bats wing and our forearm. (b)

ehavioral homologies arising for instincts inherited from a common ancestor. (c) Protein

omologies in which the sequences of amino acids that for a protein are similar because ofommon ancestry. Similarities that do not arise from common ancestry, such as the wing ofrd and the wing of an insect, are called analogies.

nds of evidence for evolution:

1. The fossil record. The facts of evolution, or the story of evolution has been piecedtogether mainly from the fossil record. Example 1 is an example of Darwins theory mexplain such evidence.

2. Homologies in l iving species. If we look carefully at living species we see surprisiand unexpected similarities (Lakatoss novel facts?) between disparate species. Thesemay range from similar bone structures in limbs of whales and bears, to similarities othe instinctive behavior of water fowl living in quite different areas of the globe, tosimilarities and differences in protein sequences in living organisms.

3. Artificial selection. Breeding experiments that show that selection can transform apopulation from one kind to another. This provides limited support for inheritability avariation. It does not provide evidence for the other postulates.

4. Experimental evidence from genetics. There is now a lot of biochemical evidenc

about DNA and the mechanisms of inheritance. This helps provide auxiliary hypothesabout the source of inheritable variation, and the mechanisms of inheritance. Forexample, it could help support Assumption 3 in Example 1.

et's at an example of evolutionary explanation.

xample 1: The evolution of horses.

Fact to be explained: In the lineage leading up to the modern genus Equus, of whthe horse is a species, the fossil record shows that the ratio of molar tooth height tolength increases over time, and that there is an accelerationin the rate of changethrough time.

Assumption 1 : The environment changed. In the Miocene period, Merychippus anddescendents abandoned the habit common to all earlier horses of browsing on leavesand took the newly evolved grasses as their main food.

Support: There is independent fossil evidence confirming that grasses evolved and



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become abundant at that time.

Assumption 2 : Engineering assumption. The high silicate content of grasses makesincreased wear per unit of vegetation consumed.

Support: Look at modern species and assume that the same physical facts apply fortime. Also note that there was another horse lineage which continued to grace on

leaves and did not evolve an elongated tooth.

Assumption 3 :Adaptationist assumption. Height to length ratio of teeth varied inhorse populations, and was an inheritable trait.

Support: Look at modern horse species to check for variation and check forinheritability through artificial breeding experiments.

Assumption 4 : Resource assumption. There were greater food resources available pindividual for those horses able to grace on the newly evolved grasses.

Support: It is almost a matter of logic to say that a horse that can eat leaves or grahas more food available to it than a horse that can only eat leaves.

Assumption 5 : Co-evolution assumption. Grass continued to be a viable food resoudespite the grazing of the new horse species. That is, the grasses managed to survivthis grazing assault.

Support: Look at fossil evidence for grasses; compare "grazability" of modern grass

emarks:

1. It is very hard to think of all the auxiliary assumptions need to deductively entail thefact to be explained.

2. Most of the assumptions have independent sources of support. It will not matter if soof the assumptions have no independent support, since some degree of accommodat

is allowed.3. Some of the assumptions talk about other instances of evolution. Does this beg the

question? No, at worst it shows that the explanations need to be evaluated as a whoThat is why Darwin's Originwas convincing in a way that previous arguments forevolution were not--it tied together many different explanations that appealed to thesame core assumptions.

4. What matters is that various facts are tied together in a surprisingly tidy way, which hard to explain as "arising from chance".



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Figure 1: Phylogeny based on differences in the protein sequence ofcytochrome c in organisms ranging from Neurosporamold to humans.

"The Theory of Evolution: Patterns and rates of species evolution: MOLECULAREVOLUTION: The molecular clock of evolution." Britannica Online.

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Figure 2: Rate of nucleotide substitution over paleontological time. Each dot marks(1) the point at which a pair of species diverged from a common ancestor and (2) thenumber of nucleotide substitutions, or protein changes, that have occurred since thedivergence. The solid line drawn from the origin to the outermost dot gives theaverage rate of substitution.

From F.J. Ayala, E. McMullin (ed.), Evolution and Creation(1985)

"The Theory of Evolution: Patterns and rates of species evolution: MOLECULAREVOLUTION: The molecular clock of evolution." Britannica Online.

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ESTIGES OF EVOLUTION: "Human and other nonaquatic embryos exhibit gill slits evenough they never breathe through gills. These slits are found in the embryos of all

ertebrates because they share as common ancestors the fish in which these structures firsvolved. Human embryos also exhibit by the fourth week of development a well-defined taihich reaches maximum length when the embryo is six weeks old. Similar embryonic tails aund in other mammals, such as dogs, horses, and monkeys; in humans, however, the tai

ventually shortens, persisting only as a rudiment in the adult coccyx."The Theory of Evolution: The evidence for evolution: EMBRYONIC DEVELOPMENT ANDESTIGES" Britannica Online.

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OGEOGRAPHY: "Darwin also saw a confirmation of evolution in the geographic distributioplants and animals, and later knowledge has reinforced his observations. For example,ere are about 1,500 species ofDrosophilavinegar flies in the world; nearly one-third of th

ve in Hawaii and nowhere else, although the total area of the archipelago is less than one-wentieth the area of California. There are also in Hawaii more than 1,000 species of snailsnd other land mollusks that exist nowhere else. This unusual diversity is easily explained bvolution. The Hawaiian Islands are extremely isolated and have had few colonizers; those

pecies that arrived there found many unoccupied ecological niches, or local environmentsited to sustain them and lacking predators that would prevent them from multiplying. Insponse, they rapidly diversified; this process of diversifying in order to fill in ecological niccalled adaptive radiation."

The Theory of Evolution: The evidence for evolution: BIOGEOGRAPHY" Britannica Online.http://www.eb.com:180/cgi-bin/g?DocF=macro/5002/24/10.html>

OLECULAR EVOLUTION: A remarkable uniformity exists in the molecular components ofganisms--in the nature of the components as well as in the ways in which they are

ssembled and used. In all bacteria, plants, animals, and humans, the DNA comprises afferent sequence of the same four component nucleotides, and all of the various proteins nthesized from different combinations and sequences of the same 20 amino acids, althouveral hundred other amino acids do exist. The genetic "code" by which the information

ontained in the nuclear DNA is passed on to proteins is everywhere the same. Similaretabolic pathways are used by the most diverse organisms to produce energy and to makp the cell components.

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his unity reveals the genetic continuity and common ancestry of all organisms. There is noher rational way to account for their molecular uniformity when numerous alternativeructures are equally likely. The genetic code may serve as an example. Each particularquence of three nucleotides in the nuclear DNA acts as a pattern, or code, for theoduction of exactly the same amino acid in all organisms. This is no more necessary thanfor a language to use a particular combination of letters to represent a particular reality. found that certain sequences of letters--planet, tree, woman--are used with identical

eanings in a number of different books, one can be sure that the languages used in thoseooks are of common origin.

enes and proteins are long molecules that contain information in the sequence of theiromponents in much the same way as sentences of the English language contain informatiothe sequence of their letters and words. The sequences that make up the genes are pass

n from parents to offspring, identical except for occasional changes introduced by mutatioo illustrate, assume that two books are being compared; both books are 200 pages long aontain the same number of chapters. Closer examination reveals that the two books are

entical page for page and word for word, except that an occasional word--say one in 100-fferent. The two books cannot have been written independently; either one has been copom the other or both have been copied, directly or indirectly, from the same original bookmilarly, if each nucleotide is represented by one letter, the complete sequence of nucleotithe DNA of a higher organism would require several hundred books of hundreds of pagesth several thousand letters on each page. When the "pages" (or sequence of nucleotides)ese "books" (organisms) are examined one by one, the correspondence in theetters" (nucleotides) gives unmistakable evidence of common origin.

he arguments presented above are based on different grounds, although both attest tovolution. Using the alphabet analogy, the first argument says that languages that use theme dictionary--the same genetic code and the same 20 amino acids--cannot be ofdependent origin. The second argument, concerning similarity in the sequence of nucleotthe DNA or the sequence of amino acids in the proteins, says that books with very similaxts cannot be of independent origin.

he evidence of evolution revealed by molecular biology goes one step further. The degreemilarity in the sequence of nucleotides or of amino acids can be precisely quantified. For

xample, cytochrome c (a protein molecule) of humans and chimpanzees consists of the sa04 amino acids in exactly the same order; but differs from that of rhesus monkeys by onemino acid, that of horses by 11 additional amino acids, and that of tuna by 21 additionalmino acids. The degree of similarity reflects the recency of common ancestry. Thus, theferences from comparative anatomy and other disciplines concerning evolutionary historyn be tested in molecular studies of DNA and proteins by examining their sequences of

ucleotides and amino acids.

he authority of this kind of test is overwhelming; each of the thousands of genes and



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ousands of proteins contained in an organism provides an independent test of thatganism's evolutionary history. Not all possible tests have been performed, but many

undreds have been done, and not one has given evidence contrary to evolution. There isobably no other notion in any field of science that has been as extensively tested and asoroughly corroborated as the evolutionary origin of living organisms.

The Theory of Evolution: The evidence for evolution: MOLECULAR BIOLOGY" Britannicanline.

omology , in biology, similarity of the structure, physiology, or development of differentpecies of organisms based upon their descent from a common evolutionary ancestor.omology is contrasted with analogy, which is a functional similarity of structure based notpon common evolutionary origins but upon mere similarity of use. Thus the forelimbs of sudely differing mammals as humans, bats, and deer are homologous; the form of

onstruction and the number of bones in these varying limbs are practically identical, andpresent adaptive modifications of the forelimb structure of their common early mammalia

ncestors. Analogous structures, on the other hand, can be represented by the wings of bir

nd of insects; the structures are used for flight in both types of organisms, but they have ommon ancestral origin at the beginning of their evolutionary development. A 19th-centuritish biologist, Sir Richard Owen, was the first to define both homology and analogy inecise terms.omology" Britannica Online.http://www.eb.com:180/cgi-bin/g?DocF=micro/275/65.html>

Figure 3: The labellum of

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the mirror ophrys (Ophrysspeculum). The colouringso closely resembles that othe female wasp Colpaaureathat males of thespecies are attracted to thflower and pick up pollen

during their attempts atcopulation.

E.S. Ross

OBZHANSKY: Between 1920 and 1935, mathematicians and experimentalists began layinge groundwork for a theory combining Darwinian evolution and Mendelian genetics. Startins career about this time, Dobzhansky was involved in the project almost from its inceptions bookGenetics and the Origin of Species(1937) was the first substantial synthesis of the

bjects and established evolutionary genetics as an independent discipline. Until the 1930se commonly held view was that natural selection produced something close to the best of

ossible worlds and that changes would be rare and slow and not apparent over one life spagreement with the observed constancy of species over historical time.

obzhansky's most important contribution was to change this view. In observing wildopulations of the vinegar fly Drosophila pseudoobscura, he found extensive geneticariability. Furthermore, about 1940 evidence accumulated that in a given local populationome genes would regularly change in frequency with the seasons of the year. For example



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ertain gene might appear in 40 percent of all individuals in the population in the spring,crease to 60 percent by late summer at the expense of other genes at the same locus, anturn to 40 percent in overwintering flies. Compared to a generation time of about oneonth, these changes were rapid and effected very large differences in reproductive fitnesse various types under different climatic conditions. Other experiments showed that, in faces of mixed genetic makeup (heterozygotes) were superior in survival and fertility to purepes.

Dobzhansky, Theodosius" Britannica Online.http://www.eb.com:180/cgi-bin/g?DocF=micro/173/58.html>

NDUSTRIAL MELANISM: Melanism refers to the deposition of melanin in the tissues of livinnimals. The chemistry of the process depends on the metabolism of the amino acid tyrosine absence of which results in albinism, or lack of pigmentation. Melanism can also occur

athologically, as in a malignant melanoma, a cancerous tumour composed of melanin-gmented cells.

elanic pigmentation is advantageous in many ways: (1) It is a barrier against the effects oe ultraviolet rays of sunlight. On exposure to sunlight, for example, the human epidermis

ndergoes gradual tanning as a result of an increase in melanin pigment. (2) It is aechanism for the absorption of heat from sunlight, a function that is especially important

old-blooded animals. (3) It affords concealment to certain animals that become active inwilight. (4) It limits the incidence of beams of light entering the eye and absorbs scattered

ht within the eyeball, allowing greater visual acuity. (5) It provides resistance to abrasionecause of the molecular structure of the pigment. Many desert-dwelling birds, for exampleave black plumage as an adaptation to their abrasive habitat.

ndustrial" melanism has occurred in certain moth populations, in which the predominantoloration has changed pale gray to dark-coloured individuals. This is a striking example ofpid evolutionary change; it has taken place in less than 100 years. It occurs in moth specat depend for their survival by day on blending into specialized backgrounds, such ashened tree trunks and boughs. Industrial pollution, in the form of soot, kills lichens andackens the trees and ground, thus destroying the protective backgrounds of light-colouredoths, which are rapidly picked off and eaten by birds. Melanic moths, by their camouflageen become selectively favoured. "Industrial" melanic moths have arisen from recurrent

utations and have spread via natural selection.melanin" Britannica Online.http://www.eb.com:180/cgi-bin/g?DocF=micro/385/80.html>

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reationism

he Creationist Debate

ast modified on Sunday, October 11, 1998, by Malcolm R. Forster

ackground: Creationists are happy with either of two claims: 1) Creationism is not a

ience, and neither is evolutionary theory (which should not be taught in schools), or 2)volutionary theory is a science but so is creationism (which should be taught in schools alode evolutionary theory). They would be happier with 1) but will settle for 2). In recent yeanti-creationists have concentrated on blocking arguments to the second conclusion.

use's criteria for science

1. Science looks for patterns in nature, order, and natural regularities (laws).2. Science is explanatory, and the use of natural regularities is necessary for this purpo

3. Science makes predictions, and the use of natural regularities is necessary for thispurpose.

4. Science looks for testability. This has two aspects. (a) Confirmation, or positive suppofor the theory. (b) a theory must be open to possible falsification. E.g., if a planet wediscovered going in squares, then the laws would have been shown to be incorrect.

5. Science is tentative. A scientist must be prepared to reject his theory.6. Science should strive for simplicity and unification.7. Scientists should be intellectually honest.

riticismsand Comments:

a. It is not clear to me why natural regularity is necessary for explanation. Nor is clear to me that explanation is necessary for science, although if science is ofteexplanatory.

b. In 4, Ruse should not claim that theories are open to logical falsification. He neonly insist that the theories modelsare open to falsification. Theories are andshould be rejected, but that is covered 5.

c. There is no mention of the distinction between prediction and accommodation

which I think is important.d. The emphasis on natural laws plays an important role in Ruse's argument

because he quotes two different creationists, who emphasize that the processused by God in the act of creation are now not operating in the natural universHowever, I do not see why science should care about the difference betweennatural and unnatural laws. Show me an unnatural law and I will make goodscientific predictions and explanations.

audan's complaints



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A. Creationism does make testable empirical assertions; e.g., that the earth is 6,0to 20,000 year old, and most of the features of the earth's surface are diluvial(arising for the great flood). They are testable, and they have failed those testf. astrology.)

B. Creationists have changed their views.C. To say that science is a matter of natural law is rather fuzzy. Darwinism was

accepted by many scientists well before the laws of genetics were known.Continental drift was accepted before the mechanism was understood. Smokinaccepted as a cause of cancer, even though the mechanism is still not fullyunderstood.

D. Ruses standards of testability and revisability are exceedingly weak. They coube satisfied by the declaration "I will abandon creationism if we find a livingspecimen between man and the apes." Exceedingly unlikely, but strong enougfor falsifiability.

E. The key issue, according to Laudan, is whether evolutionary theory is better

supported by the evidence than creationism. Debating the scientific status of ttheories is a red herring.

rguments that Creationism is a Pseudoscience (Kitcher)

rgument 1 : Scientific theories make predictions (= observational consequences deducedom the theory). If the predictions prove to be false, then the theory is false. That is,

ientific theories are falsifiable (the Popperian demarcation criterion). Creationist theory is lsifiable. Therefore creationist theory is not science.

bjection: Predictions are not deduced from scientific theories alone. Therefore, if theediction prove false, the theory is not falsified. Thus, a key premise in the argument is fal

rgument 2 : Scientific theories together with auxiliary assumptions form models. Predictioe deducible from models. Scientific models are falsifiable. Creationist models are notlsifiable. Therefore creationism is not a science.

bjection: (Kitcher 1982, "Believing Where We Cannot Prove" (reading 72), p. 66) Imaginat we want to expose some self-styled spiritual leader as a fraud. We point out that theacher's central doctrine "Quietness is wholeness in the center of stillness" is unfalsifiable.all this doctrine D. But when it is coupled with other statements, it produces observationaonsequences. For instance, let O be any observational statement. Then D combined with "then O" has the observational consequence O. So, there are models of the "theory" (M =

D, if D then O}) that are falsifiable. In other words, this criterion lets in too much, and it



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ould be easy for creationists to use it to argue that creationism is a science.

rgument 3 : (Kitcher's) In genuine science, auxiliary hypotheses are independently testedientific theories tend to be unified, and scientific theories suggest new lines of investigatio

nd new models (fecundity). Creationism does not display this cluster of features. Thereforeationism is not a science.

bjection: While I agree that these features mark a difference between genuine science aeationism, it is not clear why these features of science are relevant to the purpose of scies a source of knowledge. This is not really an objection, but it does suggest that thegument is incomplete.

rgument 4 : (Mine) Science succeeds at more than accommodating experience. Its modecceed at anticipatingfacts not used in the construction of the models. While creationism

asily accommodate the facts, it is not very successful in anticipating new facts in the requinse (there are some small exceptions to this, so it is a matter of degree).

ote 1: This gets around the objection to argument 2 because a model of the form {D, if Den O} will not predict a new observation O'. One can merely add a new auxiliary assu

Philosophy and the Sciences - Phil. Sci. Course

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