| DEDUCTION is a reasoning process
that proceeds from a general statement or a general law and leads
to a specific and necessary conclusion.
The CATEGORICAL SYLLOGISM is a structured
deduction.
CATEGORICAL STATEMENTS place their subjects into larger classes or
categories.
A categorical syllogism has three parts:
I. MAJOR PREMISE -- a proposition which
states that ALL members of a given category are included
in a larger category.
II. MINOR PREMISE -- a proposition identifying
a PARTICULAR CASE as a member of the general class.
III. CONCLUSION -- states that WHAT IS
TRUE OF ALL members MUST BE TRUE
OF
ONE member of the general class.
THE SYLLOGISM AS A FORMULA:
Major Premise:
A = B
All CATS are FURRY ANIMALS.
Minor Premise:
C = A
MORRIS is a CAT.
Conclusion:
C = B
Therefore, MORRIS is a FURRY ANIMAL.
TESTS FOR VALIDITY
VALIDITY is concerned with the STRUCTURE
of the argument.
TRUTH is concerned with the FACTUAL CONTENT of the argument.
RULE 1: The statement of the Major Premise MUST be clear and precise.
RULE 2: There must be THREE and ONLY THREE terms in a categorical
syllogism.
RULE 3: Only one premise can be negative.
And if either premise is negative, then the conclusion
must be negative.
RULE 4: The relationships among all three terms of a categorical syllogism
must be so definite and certain as to allow only one possible conclusion.
RULE 4a: In a positive categorical syllogism, the term
which appears in both the major and
minor premises must be the category inone premise
and the subject in the other.
RULE 4b: In a negative categorical syllogism, the term
which appears
in both the major and minor premises must be the category
in the positive premise.
OTHER FORMS OF THE SYLLOGISM
ALTERNATIVE SYLLOGISMS (EITHER/OR)
-- Alternative syllogisms are easily identifiable because
the major premise will always contain the two key terms either
and or.
The EXCLUSIVE ALTERNATIVE SYLLOGISM presents alternatives of which
ONLY ONE CAN BE TRUE.
The HYPOTHETICAL SYLLOGISM presents
a SET OF CONDITIONS which, if met, will cause a SPECIFIC and NECESSARY
RESULT. (IF . . . THEN)
The Major Premise states conditions & results ( If A, then
B).
The Minor Premise demonstrates satisfaction of the conditions
(A).
The Conclusion reaffirms the results (B).
OTHER DEDUCTIVE FORMS
The ENTHYMEME is an ABBREVIATED form
of the syllogism used in everyday discourse and based upon unexpressed
but commonly shared assumptions.
The CHAIN OF DEDUCTION is a complex
series of deductions of which only the conclusion is expressed. |
