A System of Logic: Ratiocinative and Inductive, 7th Edition, Vol. I — John Stuart Mill — John Shaqi
A System of Logic: Ratiocinative and Inductive, 7th Edition, Vol. I
John Stuart Mill · en
§ 2. On examining, then, these two general formulæ, we find that in
both of them, one premise, the major, is an universal proposition; and
according as this is affirmative or negative, the conclusion is so too.
All ratiocination, therefore, starts from a _general_ proposition,
principle, or assumption: a proposition in which a predicate is
affirmed or denied of an entire class; that is, in which some attribute,
or the negation of some attribute, is asserted of an indefinite number
of objects distinguished by a common characteristic, and designated in
consequence, by a common name.
The other premise is always affirmative, and asserts that something
(which may be either an individual, a class, or part of a class)
belongs to, or is included in, the class respecting which something was
affirmed or denied in the major premise. It follows that the attribute
affirmed or denied of the entire class may (if that affirmation or
denial was correct) be affirmed or denied of the object or objects
alleged to be included in the class: and this is precisely the assertion
made in the conclusion.
Whether or not the foregoing is an adequate account of the constituent
parts of the syllogism, will be presently considered; but as far as it
goes it is a true account. It has accordingly been generalized, and
erected into a logical maxim, on which all ratiocination is said to be
founded, insomuch that to reason, and to apply the maxim, are supposed
to be one and the same thing. The maxim is, That whatever can be
affirmed (or denied) of a class, may be affirmed (or denied) of
everything included in the class. This axiom, supposed to be the basis
of the syllogistic theory, is termed by logicians the _dictum de omni et
nullo_.