A System of Logic, Ratiocinative and Inductive (Vol. 1 of 2)
John Stuart Mill · en
The other premiss 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 premiss. It follows that the attribute affirmed or
denied of the entire class may (if there was truth in that affirmation or
denial) 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_.
This maxim, however, when considered as a principle of reasoning, appears
suited to a system of metaphysics once indeed generally received, but
which for the last two centuries has been considered as finally abandoned,
though there have not been wanting, in our own day, attempts at its
revival. So long as what were termed Universals were regarded as a
peculiar kind of substances, having an objective existence distinct from
the individual objects classed under them, the _dictum de omni_ conveyed
an important meaning; because it expressed the intercommunity of nature,
which it was necessary on that theory that we should suppose to exist
between those general substances and the particular substances which were
subordinated to them. That everything predicable of the universal was
predicable of the various individuals contained under it, was then no
identical proposition, but a statement of what was conceived as a
fundamental law of the universe. The assertion that the entire nature and
properties of the _substantia secunda_ formed part of the properties of
each of the individual substances called by the same name; that the
properties of Man, for example, were properties of all men; was a
proposition of real significance when man did not _mean_ all men, but
something inherent in men, and vastly superior to them in dignity. Now,
however, when it is known that a class, an universal, a genus or species,
is not an entity _per se_, but neither more nor less than the individual
substances themselves which are placed in the class, and that there is
nothing real in the matter except those objects, a common name given to
them, and common attributes indicated by the name; what, I should be glad
to know, do we learn by being told, that whatever can be affirmed of a