Elements of the philosophy of the human mind. By Dugald Stewart. Rev. and abridged, with critical and explanatory notes, for the use of colleges and schools. By Francis Bowen ...

408 REASONTING AND DEDUCTIVE EVIDENCE.
Locke's language, in various parts of his Essay, seems to accord
with the same opinion. 6 Every step in reasoning," he observes,
"that produces knowledge, has intuitive certainty; which, when
the mind perceives, there is no more required but to remember
it, to make the agreement or disagreement of the ideas, concerning which we inquire, visible and certain. This intuitive perception of the agreement or disagreement of the intermediate
ideas, in each step and progression of the demonstration, must
also be carried exactly in the mind, and a man must be sure that
no part is left out; which, in long deductions, and in the use of
many proofs, the memory does not always so readily and exactly
retain; therefore it comes to pass, that this is more imperfect
than intuitive knowledge, and men embrace often falsehood for
demonstrations."
The same doctrine is stated elsewhere by M3r. Locke, more
than once, in terms equally explicit; and yet his language
occasionally favors the supposition, that, in its deductive processes, the mind exhibits some modification of reason essentially
distinct from intuition. The account, too, which he has given
of their respective provinces, affords evidence that his notions
concerning them were not sufficiently precise and settled.
"'When the mind," says he, " perceives the agreement or disagreement of two ideas immediately by themselves, without the
intervention of any other, its knowledge may be called intuitive. When it cannot so bring its ideas together as, by their
immediate comparison, and, as it were, juxtaposition, or application one to another, to perceive their agreement or disagreement, it is fain, by the intervention of other ideas, (one or
more as it happens,) to discover the agreement or disagreement
which it searches; and this is that which we call reasoning."
According to these definitions, supposing the equality of two
lines, A and B, to be perceived immediately, in consequence of
their coincidence, the judgment of the mind is intuitive. Supposing A to coincide with B, and B with C; the relation between A and C is perceived by reasoning. Nor is this a hasty
inference from Locke's accidental language. That it is perfectly agreeable to the foregoing definitions, as understood by