A Class Room Logic: Deductive and Inductive, with Special Application to the Science and Art of TeachingMcNair, George Hastings
Philosophy
A Class Room Logic: Deductive and Inductive, with Special Application to the Science and Art of Teaching
McNair, George Hastings
Logic
(2) All men are rational beings,
No tree is a rational being,
――――――――――――――――――――――――――――
∴ No trees are men.
(3) All good citizens are law abiding,
All good citizens vote,
――――――――――――――――――――――――――――――――――
∴ Some who vote are law abiding.
I recall that the three terms are the middle, the major and the minor,
and that the “middle” does not occur in the conclusion, whereas the
“major” is always the predicate and the “minor” the subject of the
conclusion. The symbols M, G and S being the initial letters of middle,
greater and smaller, I make use of these in designating the three terms,
as the following will illustrate:
M G
(1) All fixed stars twinkle,
S M
Vega is a fixed star,
――――――――――――――――――――――――
S G
∴ Vega twinkles.
“Twinkles” being the predicate of the conclusion is designated as being
the major term by putting the letter G above it. Then “G” is placed
above the term “twinkle” in the first premise.
“S” is placed above the subject of the conclusion to indicate that it
is the minor term. “S” is also placed above “Vega,” the minor term, as
found in the second premise.
The remaining term, “fixed stars,” must be the middle term, therefore
I place “M” above it. The fact that “fixed star” does not occur in the
conclusion verifies this.
Using only the symbols, the syllogism takes this form:
All M is G
S is M
――――――
∴ S is G
Using the symbols to represent the other syllogisms, we have
(2) All G is M
No S is M
―――――――――
∴ No S is G
(3) All M is G
All M is S
――――――
∴ Some S is G
(1b) Indicate by symbols the three terms of the following syllogisms:
(1) No trees are men,
All rational beings are men,
――――――――――――――――――――――――――――
∴ No rational being is a tree.
(2) All men have the power of speech,
You are a man,
―――――――――――――――――――――――――――――――――
∴ You have the power of speech.
(3) Some men are wise,
All men are rational,
―――――――――――――――――――――
∴ Some rational beings are wise.
(2a) Illustrate by syllogism the fallacy of undistributed middle. An
easy way is to use _the middle term as the predicate of two A premises_.
This yields the fallacy because an A proposition does not distribute
the predicate.
The illustration: distributed terms underscored.
All true teachers are students,
―――――――――――――
All scholars are students,
――――――――
――――――――――――――――――――――――――――――――
∴ All scholars are true teachers.
――――――――
(2b) Give two illustrations of undistributed middle.
(3a) Give syllogistic illustrations of the fallacies of illicit major
and minor.
_Illicit Major._
Public-domain text, read in full here on John Shaqi.
Reviews
Reviews
No reviews yet
Be the first to share your thoughts on this work.
Elsewhere in the archive
Join the Discussion
Join the discussion
Sign in to leave a comment or review.
Sign InorCreate an account