A System of Logic, Ratiocinative and Inductive (Vol. 1 of 2)
John Stuart Mill · en
there can be no ground for making the assumption in that case which does
not exist in every other; and if you deny the assumption as a general
truth, you deny the right to make it in the particular instance.
There are, undoubtedly, the most ample reasons for stating both the
principles and the theorems in their general form, and these will be
explained presently, so far as explanation is requisite. But, that
unpractised learners, even in making use of one theorem to demonstrate
another, reason rather from particular to particular than from the general
proposition, is manifest from the difficulty they find in applying a
theorem to a case in which the configuration of the diagram is extremely
unlike that of the diagram by which the original theorem was demonstrated.
A difficulty which, except in cases of unusual mental power, long practice
can alone remove, and removes chiefly by rendering us familiar with all
the configurations consistent with the general conditions of the theorem.
§ 4. From the considerations now adduced, the following conclusions seem
to be established. All inference is from particulars to particulars:
General propositions are merely registers of such inferences already made,
and short formulæ for making more: The major premiss of a syllogism,
consequently, is a formula of this description: and the conclusion is not
an inference drawn _from_ the formula, but an inference drawn _according_
to the formula: the real logical antecedent, or premisses, being the
particular facts from which the general proposition was collected by
induction. Those facts, and the individual instances which supplied them,
may have been forgotten; but a record remains, not indeed descriptive of
the facts themselves, but showing how those cases may be distinguished
respecting which the facts, when known, were considered to warrant a given
inference. According to the indications of this record we draw our
conclusion; which is, to all intents and purposes, a conclusion from the
forgotten facts. For this it is essential that we should read the record
correctly: and the rules of the syllogism are a set of precautions to
ensure our doing so.