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 ...

EXTERNAL PERCEPTION. 33
6"Two thousand years after Plato,"' (continues Dr. Reid,)
J 3r. Locke, who studied the operations of the human mind so
much, and with so great success, represents our manner of perceiving external objects by a similitude very much resembling
that of the cave. M oi{ethinks,' says he, the understanding is
not much unlike a closet, wholly shut from light, with only some
little opening left, to let in external visible resemblances or ideas
of things without. Would the pictures coming into such a dark
room but stay there, and lie so orderly as to be found upon occasion, it would very much resemble the understanding of a
man, in reference to all objects of sight, and the ideas of
them.'
" Plato's subterranean cave, and Mir. Locke's dark closet,
may be applied with ease to all the systems of perceptions that
have been invented: for they all suppose, that we perceive not
external objects immediately; and that the immediate objects of
perception are only certain shadows of the external objects.
Those shadows, or images, which we immediately perceive, were
by the ancients called species, forms, phantasms. Since the time
of Des Cartes, they have commonly been called ideas; and by
gMr. Hume, impressions. But all philosophers, from Plato to
Mr. Hume, agree in this, that we do not perceive external objects immediately; and that the immediate object of perception
must be some image present to the mind." On the whole, Dr.
Reid remarks, "that in their sentiments concerning perception,
there appears an uniformity which rarely occurs upon subjects
of so abstruse a nature."
Objections to this doctrine of mediate perception. - The very
short and imperfect view we have now taken of the common
theories of perception, is almost sufficient, without any commentary, to establish the truth of the two general observations formerly made; for they all evidently proceed on a supposition,
suggested by the phenomena of physics, (1.) that there must of'
necessity exist some medium of communication between the objects of perception and the percipient mind; and they all indicate a secret conviction in their authors, (2.) of the essential dis.
tinction between mind and matter; which, although not ren