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 ...

48 EXTERNAL PERCEPTION.
pressions on our organs of sense are necessary to awaken the
mind to a consciousness of its own existence, and to give rise to
the exercise of its various faculties; yet all this might have happened without our having any knowledge of the qualities, or even
of the existence, of the material world. To facilitate the admission of this proposition, let us suppose a being formed in every
other respect like man; but possessed of no senses, excepting
those of hearing and smelling. I mlake choice of these two
senses, because it is obvious, that, by means of them alone, we
never could have arrived at the knowledge of the primary qualities of matter, or even of the existence of things external. All
that we could possibly have inferred from our occasional sensations of smell and sound, would have been that there existed
some unknown cause by which they were produced.
Let us suppose, then, a particular sensation to be excited in
the mind of such a being. The moment this happens, he must
necessarily acquire the knowledge of two facts at once: that of
the existence of the sensation; and that.of his own existence, as
a sentient being. After the sensation is at an end, he can remember he felt it; he can conceive that he feels it again. If he
has felt a variety of different sensations, he can compare them
together in respect of the pleasure or the pain they have afforded him; and will naturally desire the return of the agreeable sensations, and be afraid of the return of those which were
painful. If the sensations of smell and sound are both excited
in his mind at the same time. he can attend to either of them he
chooses, and withdraw his attention from the other; or he can
withdraw his attention from both, and fix it on some sensation
lie has felt formerly. In this manner, he might be led, merely
by sensations existing in his mind, and conveying to him no information concerning matter, to exercise many of his most important faculties; and amidst all these different modifications
and operations of his mind, he would feel, with irresistible conviction, that they all belong to one and the same sentient and
intelligent being; or, in other words, that they are all modifications and operations of himself. I say nothing, at present, of
the various simple notions, (or simple ideas, as they are corn