Logic – The study of methods and principles used to distinguish Conversion Obversion Contraposition
correct from incorrect reasoning
A Some P is S
Proposition – An assertion that some is or is not the case; all No S is non-P All non-P is non-S
(Limitation)
propositions are either true or false
Statement – The meaning of declarative sentence at a particular time, E Some non P is not non S
No P is S All S is non-P
synonymous to proposition. (limitation)
Inference – A process of linking propositions by affirming one
I (not valid)
proposition on the basis of one or more other propositions Some P is S Some S is not non P
Argument – A structured group of propositions, reflecting an
inference O Some non-P is not non S
(not valid) Some S is non P
Premise – A proposition used in an argument to support some other
proposition
Conclusion – The proposition in an argument that the other Major term – Predicate of the conclusion and appears in the first
propositions, the premises, support. premise
Fundamental principle concerning the relationship of truth and Minor term – Subject of the conclusion
validity of arguments – The truth and falsity of an argument’s
conclusion does not by itself determine the validity or invalidity of that Middle term – Appears in both premises
argument.
Deductive argument – An argument that claims to establish its
conclusion conclusively Figure - 1 Figure – 2 Figure – 3 Figure - 4
Inductive argument – An argument that claims to support its M–P P–M M–P P–M
conclusion only with some degree of probability
S–M S–M M–S M–S
Categorical proposition – A proposition used in deductive arguments
that asserts a relationship between one category and some other
category
Syllogistic Rules and Falacies
Distribution – A characterization of whether terms in a categorical
proposition refer to all members of the class designated by that term Rule Fallacy
Syllogism – Any deductive argument in which a conclusion is inferred
from two premises. Four terms
Avoid four terms
Categorical Syllogism – a deductive argument composed of three
categorical propositions, which together contain exactly three terms, Middle term must be distributed
each of which occurs in exactly two of the propositions Undistributed Middle
once
Formal nature of syllogistic argument – The validity or invalidity of
a syllogistic argument depends entirely on form. Any distributed conclusion, must
Illicit Minor/Major
be distributed in either premise
When is an argument said to be true? Truth and falsity are attributes
of individual propositions while validity and invalidity are attributes of Exclusive premise
Avoid 2 negative premises
arguments.
Immediate inference – An inference drawn directly from only one
Either premise is negative, Drawing affirmative conclusion
premise
conclusion must be negative from negative premises
Mediate inference – An inference drawn from more than one premise;
the conclusion is drawn from the first premise through the mediation 2 universal premises, no particular
Existential Fallacy
of the second conclusion may be drawn
When is a standard form categorical proposition said to be
invalid?
All S is P (A) – Subject Distributed
No S is P (E) – Subject and Predicate Distributed
Some S is P (I) – Subject and Predicate Undistributed
Some S is not P (O) – Subject Undistributed, Predicate Distributed
Contradictories – Two
propositions that cannot
both be true and both be
false
Contraries – Two
propositions that cannot
both be true and can both be
false
Subcontraries – Two
propositions that cannot both be false and can both be true
Subalteration – Universal & Particular – If the universal is true,
particular is also true
