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 ...

100 ABSTRACTION.
things present, may not give us the power to perceive things
distant, to remember things past, and to conceive things that
never existed."
What ideas correspond to general termns. - As in all the ancient metaphysical systems it was taken for granted, (probably
from the analogy of our external perceptions,) that every exertion of thought implies the existence of an object distinct from
the thinking being; it naturally occurred, as a very curious
question, What is the immediate object of our attention, when
we are engaged in any general speculation; or, in other words,
what is the nature of the idea corresponding to a general term?
When I think of any particular object which I have formerly
perceived, such as a particular friend, a particular tree, or a
particular mountain, I can comprehend what is meant by a picture or representation of such objects: and therefore the explanation given by the ideal theory of that act of the mind which
we formerly called conception, if not perfectly satisfactory, is at
least not wholly unintelligible. But what account shall we give
upon the principles of this theory, of the objects of' my thoughts,
when I employ the words friend, tree, mountain, as generic
terms? For, that all the things I have ever perceived are individuals; and consequently, that the ideas denoted by general
words, (if such- ideas exist,) are not copied from any originals
that have fallen under my observation, is not only self-evident,
but almost an identical proposition.
Opinions of the ancients on t]his subject. - In answer to this
question, the Platonists, and, at a still earlier period, the Pythagoreans taught, that although these universal ideas are not
copied from any objects perceivable by sense, yet that they
have an existence independent of the human mind, and are no
more to be confounded with the understanding, of which they
are the proper objects, than material things are to be confounded
with our powers of external perception; that as all the individuals which compose a genus must possess something in common;
and as it is in consequence of this that they belong -to that genus, and are distinguishable by the same name. this common
thing forms the essence of each, and is the object of the under