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
NOTE.――There may be some doubt in the student’s mind as to the
proposition “None but the brave deserve the fair,” really meaning
“All the fair deserve the brave.” This doubt may be better satisfied by
treating the exclusive in the second way as indicated on page 137, to
wit: Negate the subject of the exclusive, then give it the form of the
regular “E.” This results in “No not-brave persons deserve the fair,”
which, after first converting and then obverting becomes, “All the fair
deserve the brave.”
_Arguments Containing Individual Propositions._
(4) “George Washington never told a lie, but you, when tempted,
yielded with no qualms of conscience.”
Completing, and arranging logically gives:
E George Washington never told a lie,
―――――――――――――――――
A You _did_ tell a lie,
―――
E ∴ You (in this respect) are not like George Washington.
――― ―――――――――――――――――
Treated properly this argument proves to be valid; the student, however,
is apt to deal with such in this wise:
O George Washington never told a lie,
―――
I You did tell a lie,
―――
O ∴ You (in this respect) are not like George Washington.
――― ―――――――――――――――――
When placed in this mood the argument is invalid; since the major
term, which is distributed in the conclusion, is not distributed in
the premise where it occurs (_illicit major_). It is the tendency on
the part of students to classify as particular, a proposition which
has as its subject a _singular term_. Such propositions we have learned
to call _individual_. The cause of this tendency is easily explained:
Consider the propositions, (1) “This man is mortal”; (2) “Some men are
mortal”; (3) “All men are mortal.” In the first instance “_mortal_”
refers to the subject “_man_” which is narrower in significance than
“_some men_” to which “mortal” of the second proposition refers.
In consequence, it is very natural to infer that if, “_Some men are
mortal_,” is particular, then, “_This man is mortal_,” is likewise
particular. The error springs from a wrong conception of particular
as used in logic; the content of the term has little to do with
_extension_, but is chiefly concerned with _indefiniteness_. A
particular proposition is one in which the predicate refers to only
a part of an _indefinite_ subject. If the subject is referred to as
a whole, and this whole is more or less definite, then the proposition
is universal. Since “mortal” refers to the _whole_ of the definite term
“_this man_,” as positively as it refers to the whole of “_all men_,”
there is as much justification in calling the _first_ proposition
universal as there is in calling the _third_ universal. _It may be
remembered, then, that logicians class as universal all individual
propositions._
_Arguments Containing Partitive Propositions._
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