A System of Logic: Ratiocinative and Inductive, 7th Edition, Vol. I
John Stuart Mill · en
§ 2. A proposition being a portion of discourse in which something is
affirmed or denied of something, the first division of propositions is
into affirmative and negative. An affirmative proposition is that in
which the predicate is _affirmed_ of the subject; as, Cæsar is dead. A
negative proposition is that in which the predicate is _denied_ of the
subject; as, Cæsar is not dead. The copula, in this last species of
proposition, consists of the words _is not_, which are the sign of
negation; _is_ being the sign of affirmation.
Some logicians, among whom may be mentioned Hobbes, state this
distinction differently; they recognise only one form of copula, _is_,
and attach the negative sign to the predicate. "Cæsar is dead," and
"Cæsar is not dead," according to these writers, are propositions
agreeing not in the subject and predicate, but in the subject only. They
do not consider "dead," but "not dead," to be the predicate of the
second proposition, and they accordingly define a negative proposition
to be one in which the predicate is a negative name. The point, though
not of much practical moment, deserves notice as an example (not
unfrequent in logic) where by means of an apparent simplification, but
which is merely verbal, matters are made more complex than before. The
notion of these writers was, that they could get rid of the distinction
between affirming and denying, by treating every case of denying as the
affirming of a negative name. But what is meant by a negative name? A
name expressive of the _absence_ of an attribute. So that when we affirm
a negative name, what we are really predicating is absence and not
presence; we are asserting not that anything is, but that something is
not; to express which operation no word seems so proper as the word
denying. The fundamental distinction is between a fact and the
non-existence of that fact; between seeing something and not seeing it,
between Cæsar's being dead and his not being dead; and if this were a
merely verbal distinction, the generalization which brings both within
the same form of assertion would be a real simplification: the
distinction, however, being real, and in the facts, it is the
generalization confounding the distinction that is merely verbal; and
tends to obscure the subject, by treating the difference between two
kinds of truths as if it were only a difference between two kinds of
words. To put things together, and to put them or keep them asunder,
will remain different operations, whatever tricks we may play with
language.