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 ...

210 THE INFLUENCtI OF CASUAL ASSOCIATIONS.
extension, at the same time at which the sensation of color is
excited in the mind, we find it impossible to think of that senllsation, without conceiving extension along with it.
Another intimate association is formed in every mind between
the ideas of space and of time. When we think of an interval
of duration, we always conceive it as something analogous to a
plausibility to the ambiguity of words. When he affirms, for example,
that the smell of a rose is not in the flower, but in the mind, his proposition amounts only to this, that the rose is not conscious of the sensation
of smell; but it does not follow from 1)es Cartes' reasonings, that there is
no quality in the rose which excites the sensation of smell in the mind;which is all that any person means when he speaks of the smell of that
flower. For the word smell, like the names of all secondary qualities,
signifies twco things, a sensation in the mind, and the unknown quality
which fits it to excite that sensation. The same remark applies to that
process of reasoning by which Des Cartes attempts to prove that there is
no heat in the fire.
All this, I think, will be readily allowed with respect to smells and
tastes, and also with respect to heat and cold; concerning which, I agree
with Dr. Reid, in thinking that Des Cartes' doctrine, when cleared of that
air of mystery which it derives from the ambiguity of words, differs very
little, if at all, from the commonly received notions. But the case seems
to be different with respect to colors, of the nature of which the vulgar are
apt to form a very confused conception, which the philosophy of Des
Cartes has a tendency to correct. Dr. Reid has justly distinguished the
qetlity of color from what he calls the appearance of color, which last can
only exist in a mind. Now I am disposed to believe, that when the vulgar
speak of color, they commonly mean the appearance of color; or rather they
associate the appearance and its cause so intimately together, that they
find it impossible to think of them separately. The sensation of color
never forms one simple object of attention to the mind, like those of smell
and taste; but every time we are conscious of it, we perceive at the same
time extension and figure. Hence it is, that we find it impossible to conceive color without extension, though certainly there is no more necessary
connection between them, than between extension and smell.
From this habit of associating the two together, we are led also to assign
them the same place, and to conceive the different colors, or, to use Dr.
Reid's language, the appearance of the different colors, as something
spread over the surfaces of bodies. I own, that when we reflect on the
subject with attention, we find this conception to be indistinct, and see
clearly that the appearance of color can exist only in a mind; but still it
is some confused notion of this sort, which every man is disposed to form