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
The I proposition illustrated:
1. “Some men are wise.”
2. “Some animals are vertebrates.”
3. “Some teachers are inspiring.”
The meaning of the I proposition may be represented by two circles
intersecting each other:
Illustration: FIG. 3.
The significant feature of the diagram is the shaded part which
represents a part of the “men” circle as belonging to a part of the
“wise” circle. The unshaded part of each circle is the unknown field.
(4) _The Particular Negative or O Proposition._
_The common symbolization of the O is “Some S is not P.”_ Put in
statement form: Some of the subject is excluded from the whole of the
predicate. Here, as in the I, the same logical import must be given to
_some_; e. g., in the proposition, “Some men are not wise,” our
knowledge is confined to the group who are not wise. Whether or not the
others are wise or not-wise is unknown.
Illustrations of the O proposition:
1. “Some men are not wise.”
2. “Some laws are not just.”
3. “Some novels are not helpful.”
The significance of the O proposition may be shown by two intersecting
circles as in Fig. 4:
Illustration: FIG. 4.
A similar diagram represents the I proposition, the only difference
being in the _part shaded_. In the O proposition the investigated field
is all of the “men” circle _outside_ of the “wise” circle, while in the
I proposition the known field is that part of the “men” circle _inside_
the “wise” circle.
In comparing the four diagrams the student will note that the
affirmative propositions are _inclusive_, while the negative
propositions are _exclusive_.
(5) _The Distribution of Subject and Predicate._
_A term is said to be distributed when it is referred to as a definite
whole._
In the proposition, “All men are mortal,” the subject _all men_ is
considered as a whole. “_All_ men” stands for every specimen of the
human race; not a single one has been left out. Again, _the whole_ is
definite; any one, if he were given the time and opportunity, could
ascertain by actual count just how many “all men” represented.
It should be observed that if the word _definite_ is not incorporated
in the definition of a distributed term, there is afforded an
opportunity for error. The attending illustrations will make this clear:
1. “All the students except John and James are dismissed.”
2. “All the students except John, James, etc., are dismissed.”
The subject of the first proposition is distributed, while the subject
of the second is undistributed. Reasons: The first subject, “All the
students except John and James,” is referred to as a whole and that
whole is definite, therefore, it is distributed; the second subject,
“All the students except John, James, etc.,” is referred to as a whole,
but as the whole is not definite, the term is not distributed. Because
_all_ is the quantity sign of the second subject the casual observer
might easily be misled in designating it as a distributed term.
Public-domain text, read in full here on John Shaqi.
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