7/30/2019 Deduction and Induction.pptx
1/18
Evaluating DeductiveArgumentsCHAPTER 6
7/30/2019 Deduction and Induction.pptx
2/18
DeductionandInduction
7/30/2019 Deduction and Induction.pptx
3/18
All arguments claim to provide
support- that is, evidence orreasons- for their conclusions.
Traditionally, arguments havebeen divided into two types:
1. Deductive Argument
2. Inductive Argument
7/30/2019 Deduction and Induction.pptx
4/18
DEDUCTIVE ARGUMENT
conclusions of these arguments are
established by the premises with
absolute certainty.
each conclusion flows from its
premises with logical necessity.
This means that, given the premises, theconclusion could not be possibly false.
7/30/2019 Deduction and Induction.pptx
5/18
DEDUCTIVE ARGUMENT
Examples:
All crustaceans are arthropods.
All spiders are arthropods.Therefore, all spiders are crustaceans.
Quartz scratches glass.
Therefore, quartz is harder than glass.
7/30/2019 Deduction and Induction.pptx
6/18
Examples:
If the sun is starAnd sun has planets
Therefore, some stars have planets
All men are mortal
Socrates was a man
Socrates was mortal
7/30/2019 Deduction and Induction.pptx
7/18
INDUCTIVE ARGUMENTS
simply claim that their conclusions arelikely or probable given the premisesoffered.
Example:
Maria has good study habits and is alwaysattentive in class discussions.
She is a consistent deans lister and has neverfailed in any subject she has taken.
Therefore, it is very probable that Maria will not failin her P-101 class.
7/30/2019 Deduction and Induction.pptx
8/18
Examples:
Socrates was Greek
Most Greeks eat fish
Socrates ate fish
You have a very good friend circle
Therefore, you are very good
7/30/2019 Deduction and Induction.pptx
9/18
INDUCTIVE ARGUMENTS
Truth of the premises cannotabsolutely rule out the possibility
that the conclusion will be false.
In other words, the conclusion might
turn out to be false even thepremises are true.
7/30/2019 Deduction and Induction.pptx
10/18
INDUCTIVE ARGUMENTS
Example:
The car cant start even though there is
plenty of gasoline in the tank.
It is likely that the battery is already
exhausted.
7/30/2019 Deduction and Induction.pptx
11/18
It is sometimes said that the basic
difference between deduction andinduction is that:
INDUCTION moves from particularpremises to general conclusions.
DEDUCTION moves from generalpremises to particular conclusions.
7/30/2019 Deduction and Induction.pptx
12/18
Examples:
DEDUCTION
Three is a prime number.
Five is a prime number.
Seven is a prime number.
(particular premise)
Therefore, all odd numbers between two and eight areprime numbers.
(general conclusion)
INDUCTION
All ofJ.K.Rowlings previous books have been bestsellers.(general premise)
Therefore, her next book will probably ba a bestseller.
(particular conclusion)
7/30/2019 Deduction and Induction.pptx
13/18
Differences Between
Deductive and Inductive Reasoning
Deductive Arguments
claim that
Inductive Arguments
claim that
If the premises are
true, then theconclusion is certainlytrue.
The conclusion followsnecessarily from thepremises.
If the premises are
true, then theconclusion isprobably true.
The conclusion followsprobably from thepremises.
7/30/2019 Deduction and Induction.pptx
14/18
Differences Between
Deductive and Inductive Reasoning
Deductive Arguments
claim that
Inductive Arguments
claim that
The premises provide
conclusive evidencefor the truth of theconclusion.
The truth of thepremises guaranteesthe truth of theconclusion.
The premises provide
good evidence for thetruth of theconclusions.
The truth of thepremises makes thetruth of the conclusionlikely.
7/30/2019 Deduction and Induction.pptx
15/18
To determine whether an argument isdeductive or inductive, here are some
common indicator words:
certainly
definitelyabsolutely
conclusively
it is logically to conclude thatthis logically implies thatthis entails that
it must be the case that
DEDUCTIVEINDICATOR WORDS
7/30/2019 Deduction and Induction.pptx
16/18
probably
likelychances are
one would expect that
it is plausible to support thatit is reasonable to presume that
INDUCTIVE INDICATOR
WORDS
7/30/2019 Deduction and Induction.pptx
17/18
When no indicator words are
present to help us decidewhether an argument is
deductive or inductive, we just
have to base our judgmentonthe content of the premises
and conclusion of the
argument.
7/30/2019 Deduction and Induction.pptx
18/18
THANK YOU FORLISTENING!!!
^____________^