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Introduction to Logic - Lecture notes on
Induction and Abduction with fallacies of
induction
Philosophy and Contemporary Ideas (Liberty University)
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Introduction to Logic: Phil 201-008 Dr. Jones (Fall 2019)
•Abduction: a form of reason that argues for the truth of some theory
by showing that it is better able to account for the known data then is
any competing theory
•AKA “inference to the best explanation”
•Example: people used to believe that the Earth was at the center of the
universe. They believed this so long that when Copernicus came
forward to say that the sun was actually the enter of the universe,
everyone thought he was crazy based on their abductive reasoning
Criteria for a sound and valid argument:
•Coherence
•Factual adequacy- ability to account for all known data
•Simplicity: doesn’t involve unnecessary complexity
•Explanatory power
Oakham’s Razor:
“thou shalt not multiply entities beyond necessity”
-this means when you’re devising your theory about something, do not add
more things to it just to make it sound more complex keep it as complex
as only necessary therefor, not too simple, not too complex
* a simple theory that can explain the phenomenon is more preferable to an
overly complex one that explains the theory the same*
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•Like induction, abduction does not garuantee its conclusions but
rather raises their degree of probability
•Abduction is a form of INduction NOT DEduction
•Because abduction is a form of induction, your conclusions are not
100% garaunteed because you’re dealing with a degree of probability
•“We should not love our theories more than we love the truth. Truth
is important.” -Dr. Jones
Fallacies to Beware!
Three Formal Fallacies of Deduction:
1. Affirming the
consequent: X>Y
Y
: . X
2. Denying the
Antecedent: X>Y
~X
: . ~Y
3. Affirming the
Disjunct: X v Y
X
: . ~Y
Three Fallacies of Induction:
1. Hasty induction
2. Lazy induction
3. Forgetful induction
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