New From Causation to Mechanismsmechanism.ucsd.edu/teaching/phil12/lectures/mechanisms.pdf · 2006. 3. 9. · 1 From Causation to Mechanisms Review Experiments provide the best evidence

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From Causation to From Causation to MechanismsMechanisms

ReviewReviewExperiments provide the best evidence of a causal Experiments provide the best evidence of a causal relation, but sometimes they are not possible relation, but sometimes they are not possible

Since it is impossible physically or morally to Since it is impossible physically or morally to manipulate the independent variablemanipulate the independent variable

Two strategiesTwo strategiesProspective studiesProspective studies

Divide groups according to the independent Divide groups according to the independent variable and investigate correlation with the variable and investigate correlation with the dependent variabledependent variable

Retrospective studiesRetrospective studiesDivide group according to the dependent variable Divide group according to the dependent variable and investigate correlation with the independent and investigate correlation with the independent variablevariable

Review Review -- 22All studies of causation are beset by confoundsAll studies of causation are beset by confounds

Factors correlated with the independent variable that Factors correlated with the independent variable that may themselves be the cause of the change in the may themselves be the cause of the change in the dependent variabledependent variable

By manipulating the independent variable in an By manipulating the independent variable in an experiment, researchers reduce the risk of confoundsexperiment, researchers reduce the risk of confounds

Researchers can randomize subjects or control (lock) Researchers can randomize subjects or control (lock) procedural variables to minimize confoundsprocedural variables to minimize confounds

Prospective and retrospective experiments do not allow Prospective and retrospective experiments do not allow manipulationmanipulation

Greater risk of confounds. Try to reduce the riskGreater risk of confounds. Try to reduce the riskBy matching subjectsBy matching subjectsBy measuring possible confoundsBy measuring possible confounds

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Two limitations of causes for Two limitations of causes for sciencescience

Individual causal relations do not accomplish muchIndividual causal relations do not accomplish muchIt requires a coordinated system of causes to get It requires a coordinated system of causes to get something donesomething done

What relates causes to their effects?What relates causes to their effects?Typically there are processes intervening between Typically there are processes intervening between causes and their effectscauses and their effects

Between and within causal relations scientists look for Between and within causal relations scientists look for mechanismsmechanismsParts (entities) and operations (activities) Parts (entities) and operations (activities) organized to produce an phenomenonorganized to produce an phenomenon

The Ubiquity of Mechanisms in The Ubiquity of Mechanisms in ScienceScience

Mechanisms in physical sciencesMechanisms in physical sciencesSolar system mechanicsSolar system mechanicsMechanisms of chemical reactionsMechanisms of chemical reactions

Mechanisms in biological sciencesMechanisms in biological sciencesMechanisms of photosynthesisMechanisms of photosynthesisMechanisms of reproductionMechanisms of reproduction

Mechanisms in behavioral sciencesMechanisms in behavioral sciencesMechanisms of memory encodingMechanisms of memory encodingMechanisms of decision makingMechanisms of decision making

Mechanisms in social sciencesMechanisms in social sciencesMechanisms of consensus formationMechanisms of consensus formation

Mechanisms as Coordinated Mechanisms as Coordinated CausationCausation

Mechanisms are made of parts whose operations Mechanisms are made of parts whose operations causingcausing changes in other parts, enabling mechanisms changes in other parts, enabling mechanisms to to causecause changes in yet other thingschanges in yet other thingsMuscles in heart contract while Muscles in heart contract while valves open and shut, valves open and shut, enablingenabling

The heart to move blood The heart to move blood through arteries and veinsthrough arteries and veins

Understanding a mechanismUnderstanding a mechanismrequires experimental requires experimental procedures designed to figure out the parts, their causal procedures designed to figure out the parts, their causal operation, and how these operations are coordinated so operation, and how these operations are coordinated so that the mechanism can produce its effectthat the mechanism can produce its effect

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Designing Mechanisms Designing Mechanisms vsvsDiscovering MechanismsDiscovering Mechanisms

The challenge in engineering is to design new The challenge in engineering is to design new mechanisms that produce the phenomena we are mechanisms that produce the phenomena we are interested ininterested in

Typically, engineers begin with an objective and Typically, engineers begin with an objective and recruit parts already known to perform operationsrecruit parts already known to perform operationsTheir challenge is to discover new modes of Their challenge is to discover new modes of organization that enable the parts to together do organization that enable the parts to together do something newsomething new

Scientists do not have access to the design manuals of Scientists do not have access to the design manuals of the mechanisms operative in the natural worldthe mechanisms operative in the natural world

They must They must reverse engineerreverse engineer themthem——discover the discover the parts, the operations, and the organizationparts, the operations, and the organization

Early machines: Variations on a Early machines: Variations on a themetheme

WedgeWedge

RampRamp

Screw

Early simple machines used human energy but extended its capacity

• In these cases, shape and spatial layout explain the causal efficacy

Early machines: Variations on Early machines: Variations on another themeanother theme

LeverLever

WheelWheel

PulleyPulley

In these cases, shape and layout together with coordination of parts explains the effect

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Simple mechanisms as tools to Simple mechanisms as tools to make tasks easiermake tasks easier

Permit the performance of activities that otherwise would not be possible

Combining simple mechanismsCombining simple mechanisms

Engineering: organizing Engineering: organizing components to produce components to produce effectseffects

Common force for creating new Common force for creating new machines: warfaremachines: warfare

The Gastrophetes or belly bow, introduced around 400 BCE, designed to launch arrows further and more accurately than the traditional bow

The Oxybeles, introduced around 375 BCE, provided ever greater power and accuracy

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Common force for creating new Common force for creating new machines: warfaremachines: warfare

Ballista, introduced around 50 BCE, used more for throwing stones than arrows

Onager, developed around 350 CE, was a low cost way of launching projectiles such as clay balls with Greek fire inside

Common force for creating new Common force for creating new machines: warfaremachines: warfare

Trebuchet: a counterweighted catapult designed to throw heavy projectiles

Such as pianos!• Chris throwing Maggie’s piano in

Northern Exposure

From Simple to ComplexFrom Simple to ComplexCommon theme in both engineering and scienceCommon theme in both engineering and science

Begin with simple designs but increasingly engineer Begin with simple designs but increasingly engineer or discover more and more complex mechanismsor discover more and more complex mechanismsLarge numbers of partsLarge numbers of partsPerforming many different operationsPerforming many different operationsCoordinated in ever more complex waysCoordinated in ever more complex ways

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Nature as a machine:Nature as a machine:Rene DescartesRene Descartes

“I have described this earth and indeed the whole universe as if it were a machine: I have considered only the various shapes and movements of its parts” (Principia IV 188).

All action in the physical universe due to shape and motion of physical matter

No vacuumNo action at a distance

Magnetism: Screw-shaped particles (formed in vortices) fit into threads in iron.

“I have described this earth and indeed the whole universe as if it were a machine: I have considered only the various shapes and movements of its parts” (Principia IV 188).

All action in the physical universe due to shape and motion of physical matter

No vacuumNo action at a distance

Robert Boyle: Restorer of the Robert Boyle: Restorer of the Mechanical PhilosophyMechanical Philosophy

Introduced the name mechanical philosophy.

Air pump—adapted design of Otto von Guericke

Air molecules as springs

Boyle’s law: “the hypothesis, that supposes the pressures and expansions to be in reciprocal proportion”

Descartes: Animals Descartes: Animals as machinesas machines

Impressed by the statuary in the Royal Gardens that moved by hydraulic principles

Animal bodies are purely mechanical devices

Circulation of blood due to heating in the heart, causing the expansion of droplets of blood, which then forced their way through the arteries

Nerve transmission and brain activity purely mechanical (albeit influenced by the mind in humans)

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Humans as machinesHumans as machinesDescartes could not conceive of a mechanism that could think or use language

• Accordingly, held that the human capacity for thought was not due to a mechanism

• Rather, thought due to a non-material mind

Julien Offray de La Mettrie objected that Descartes did not go far enough—all human activities, including thinking explained in mechanical terms

• Man the Machine in 1748

Newton: Expanding the Newton: Expanding the mechanical philosophymechanical philosophy

Endorsed the mechanical philosophyLight and heat nothing but particles in motion

“I wish we could derive the rest of the phenomena of Nature by the same kind reasoning from mechanical principles, for I am induced by many reasons to suspect that they may all depend upon certain forces by which the particles of bodies, by some causes hitherto unknown, are each mutually impelled towards one another, and cohere in regular figures, or are repelled and recede from one another. These forces being unknown, philosophers have hitherto attempted the search of Nature in vain; but I hope the principles here laid down will afford some light either to this or some truer method of philosophy”

Preface to Principia

Jacques de Jacques de VaucansonVaucanson (1709(1709--1782):1782):“Moving Anatomy”“Moving Anatomy”

Mechanical duck Mechanical duck could move in the typical, wagging way of could move in the typical, wagging way of

a ducka duckeat and digest fisheat and digest fishexcrete the remains in a "natural" way excrete the remains in a "natural" way

Mechanism was driven by a weightMechanism was driven by a weight

Consisted of more than a thousand moving Consisted of more than a thousand moving parts, concealed inside the duck and the parts, concealed inside the duck and the base on which the bird stood base on which the bird stood

Besides the duck, a flute and tambourine Besides the duck, a flute and tambourine playerplayer

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Applying mechanical ideas to living Applying mechanical ideas to living organismsorganisms

Living things seem to behave in complex Living things seem to behave in complex ways that defy simple mechanical ways that defy simple mechanical explanationexplanation

Vitalists maintained that the complexity Vitalists maintained that the complexity and and purposivenesspurposiveness of biological of biological processes made mechanical explanation processes made mechanical explanation impossibleimpossible

Mechanists developed more complex Mechanists developed more complex conceptions of mechanismsconceptions of mechanisms

TropismTropismTwo principles of Jacques Loeb:Two principles of Jacques Loeb:(i) The movements of an organism to or from a center of a (i) The movements of an organism to or from a center of a stimulus are caused by action of the stimulus on the stimulus are caused by action of the stimulus on the receptors, and through these on the organs of locomotion, receptors, and through these on the organs of locomotion, in consequence of which the animal turns until its body is in consequence of which the animal turns until its body is symmetrically stimulated and an equilibrium obtained symmetrically stimulated and an equilibrium obtained between the two sides. between the two sides. (ii) These movements occur mechanically, as a result of (ii) These movements occur mechanically, as a result of physical and chemical changes in the receptors and physical and chemical changes in the receptors and effectors, with no real effort on the part of the organism. effectors, with no real effort on the part of the organism.

Designing a Designing a tropistictropistic machinemachine

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Designing a Designing a tropistictropistic machinemachine

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Characterizing mechanismsCharacterizing mechanismsParts (entities) and operations (activities) Parts (entities) and operations (activities) organized to produce a phenomenonorganized to produce a phenomenon

Start with a phenomenon of interest:Start with a phenomenon of interest:tropism of plantstropism of plantscell divisioncell divisionremembering events in one’s liferemembering events in one’s lifeincreasing worker productivityincreasing worker productivity

Describing the PhenomenonDescribing the PhenomenonBefore setting out to explain a phenomenon, need to Before setting out to explain a phenomenon, need to characterize it as accurately as possiblecharacterize it as accurately as possible

Otherwise one risks trying to explain something that Otherwise one risks trying to explain something that might not be possiblemight not be possible

An important role for purely An important role for purely observational researchobservational researchBefore seeking a mechanism by which the universe Before seeking a mechanism by which the universe continues to expand, make sure it iscontinues to expand, make sure it isBefore explaining mechanism of global warming, Before explaining mechanism of global warming, make sure it is really occurringmake sure it is really occurring

But the description of the phenomena may be But the description of the phenomena may be revisedrevisedin the process of figuring out the mechanismin the process of figuring out the mechanism

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Mechanisms have Mechanisms have working working partsparts

To understand a mechanism, one must To understand a mechanism, one must decomposedecompose itit——take it aparttake it apart

LiterallyLiterally——actually remove the parts to study them in actually remove the parts to study them in isolationisolationFigurativelyFiguratively——figure out what the parts are and what figure out what the parts are and what they do they do

In identifying components, focus both on theirIn identifying components, focus both on theirStructureStructureFunction Function

Structural components of cellsStructural components of cellsCell components tend to have boundaries (membranes) that restrict access

Components have distinctive appearances, especially when stained Worry—since things have to be manipulated to be seen, is what you see reflective of what is there?

Or is it a product of your manipulation: an artifact

What are the parts of the brain?What are the parts of the brain?Open up the skull, and you see Open up the skull, and you see a hunk of grey matter highly a hunk of grey matter highly convolutedconvoluted

What are the What are the workingworking parts of parts of the brain?the brain?

Sulci and Gyri?

Lobes?

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What are the working parts of the What are the working parts of the brain?brain?

Korbinian Brodmann (1909) assumed differences in neuron Korbinian Brodmann (1909) assumed differences in neuron type, density, layering, probably related to functiontype, density, layering, probably related to function

Delineated areas in the brains of humans and many other species

What are the working parts of the What are the working parts of the brain?brain?

With improved tools, including tools for tracing the With improved tools, including tools for tracing the connectivity of neural processes (axons and dendrites) connectivity of neural processes (axons and dendrites) modern brain modern brain mappersmappers have developed maps that seem to have developed maps that seem to correspond to functioncorrespond to function

What operations do the What operations do the components perform?components perform?

Just locating and isolating a component doesn’t reveal Just locating and isolating a component doesn’t reveal what the component doeswhat the component does

How does one figure out what these things do?

Sometimes probing a item in various ways will reveal what it does

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What operations do the What operations do the components perform?components perform?

Often one must reason backwards from what the whole Often one must reason backwards from what the whole mechanism does to what operations are needed to perform mechanism does to what operations are needed to perform that activitythat activity

Often these operations are not obviousOften these operations are not obviousReverse engineeringReverse engineeringFiguring out what task needs to be performedFiguring out what task needs to be performedUsing information about the type of operations that Using information about the type of operations that have been previously identified in similar systemshave been previously identified in similar systemsDrawing upon analogies with machines made by Drawing upon analogies with machines made by humanshumans

What are the operations in What are the operations in fermentation?fermentation?

Strategies of discovering Strategies of discovering intermediate operationsintermediate operations

Isolate possible intermediariesIsolate possible intermediariesInhibit possible intermediate processes to see if Inhibit possible intermediate processes to see if that stops the reactionthat stops the reaction——lesion experimentlesion experimentInsert possible intermediaries to see if they Insert possible intermediaries to see if they could produce the end productcould produce the end product——excitation excitation experimentexperiment

pq

r stuv w

Inhibition (lesion)

Excitation Detection

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OrganizationOrganizationThe third feature of mechanisms is that they are organized The third feature of mechanisms is that they are organized and that the organization mattersand that the organization matters

Grains of sand in a sand pile are notGrains of sand in a sand pile are notorganized: you can recombine theorganized: you can recombine thegrains at will and nothing happensgrains at will and nothing happens

In mechanisms, one part depends on others, so organization In mechanisms, one part depends on others, so organization mattersmatters

Exemplary mechanism: the Exemplary mechanism: the computercomputer

In the midIn the mid--1919thth century Charles Babbage had the idea to century Charles Babbage had the idea to mechanize computationmechanize computation

The Difference Engine

The Analytical Engine

Creating programs: Creating programs: AdaAda Byron, Byron, Countess of LovelaceCountess of Lovelace

Her mother had her trained in Her mother had her trained in mathematics so she wouldn’t be mathematics so she wouldn’t be tempted to be a poet like her fathertempted to be a poet like her father

Became friends with Babbage and Became friends with Babbage and helped sell his analytical engine to helped sell his analytical engine to Italian sponsorsItalian sponsors

Recognized the promise of a general Recognized the promise of a general computer: "developing and tabulating computer: "developing and tabulating any function whatever. . . the engine any function whatever. . . the engine [is] the material expression of any [is] the material expression of any indefinite function of any degree of indefinite function of any degree of generality and complexity." generality and complexity."

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Mechanizing computingMechanizing computing

111

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0 0 1 11

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a0 --> 1Laa1 --> 1Lcb0 --> 0Rab1 --> 1Rd

c0 --> Halt

z1 --> 0Rs

:.

Sequences of simple mechanical operations could compute any given function

A special version of such a machine could compute all computable functions: Universal Turing Machine

Actual computers: Actual computers: Army, Census Army, Census Bureau, and Bureau, and

Predicting ElectionsPredicting Elections

The question reversesThe question reversesComputers became tools for modeling mental activities: Computers became tools for modeling mental activities: designing computers to simulatedesigning computers to simulate

PerceivingPerceivingRememberingRememberingUsing languageUsing language

Do computers think?Do computers think?Remember, they were built upon the model of how the Remember, they were built upon the model of how the human mind was thought to work!human mind was thought to work!

Do humans think by carrying out the same operations in Do humans think by carrying out the same operations in the same way as computers?the same way as computers?