A System of Logic, Ratiocinative and Inductive — John Stuart Mill — John Shaqi
A System of Logic, Ratiocinative and Inductive
John Stuart Mill · en
At first sight this division has the air of an absurdity; a solemn
distinction of things into one and more than one; as if we were to divide
horses into single horses and teams of horses. And it is true that what is
called a complex (or compound) proposition is often not a proposition at
all, but several propositions, held together by a conjunction. Such, for
example, is this: Cæsar is dead, and Brutus is alive: or even this, Cæsar
is dead, _but_ Brutus is alive. There are here two distinct assertions;
and we might as well call a street a complex house, as these two
propositions a complex proposition. It is true that the syncategorematic
words _and_ and _but_ have a meaning; but that meaning is so far from
making the two propositions one, that it adds a third proposition to them.
All particles are abbreviations, and generally abbreviations of
propositions; a kind of short-hand, whereby something which, to be
expressed fully, would have required a proposition or a series of
propositions, is suggested to the mind at once. Thus the words, Cæsar is
dead and Brutus is alive, are equivalent to these: Cæsar is dead; Brutus
is alive; it is desired that the two preceding propositions should be
thought of together. If the words were, Cæsar is dead, _but_ Brutus is
alive, the sense would be equivalent to the same three propositions
together with a fourth; “between the two preceding propositions there
exists a contrast:” viz., either between the two facts themselves, or
between the feelings with which it is desired that they should be
regarded.
In the instances cited the two propositions are kept visibly distinct,
each subject having its separate predicate, and each predicate its
separate subject. For brevity, however, and to avoid repetition, the
propositions are often blended together: as in this, “Peter and James
preached at Jerusalem and in Galilee,” which contains four propositions:
Peter preached at Jerusalem, Peter preached in Galilee, James preached at
Jerusalem, James preached in Galilee.
We have seen that when the two or more propositions comprised in what is
called a complex proposition are stated absolutely, and not under any
condition or proviso, it is not a proposition at all, but a plurality of
propositions; since what it expresses is not a single assertion, but
several assertions, which, if true when joined, are true also when
separated. But there is a kind of proposition which, though it contains a
plurality of subjects and of predicates, and may be said in one sense of
the word to consist of several propositions, contains but one assertion;
and its truth does not at all imply that of the simple propositions which
compose it. An example of this is, when the simple propositions are
connected by the particle _or_; as, either A is B or C is D; or by the
particle _if_; as, A is B if C is D. In the former case, the proposition
is called _disjunctive_, in the latter, _conditional_: the name
_hypothetical_ was originally common to both.