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 ...

94 ABSTRACTIONo
species; which men in their situation would no more be led to
form, than a person who had only seen one individual of each
species, would think of an appellative to express both, instead
of applying a proper name to each. In consequence of the
variety of birds, it appears, that they had a generic name comprehending all of them, to which it was not unnatural for them
to refer any new animal they met with.
The process of abstraction explained. -The classification of
different objects supposes a power of attending to some of their
qualities or attributes, without attending to the rest; for no two
objects are to be found without some specific difference; and no
assortment or arrangement can be formed among things not
perfectly alike, but by losing sight of their distinguishing peculiarities, and limiting the attention to those attributes which belong to them in common. Indeed, without this power of attending separately to things which our senses present to us in a state
of union, we never could have had any idea of nzumber; for, before we can consider different objects as forming a multitude, it
is necessary that we should be able to apply to all of them one
common name; or, in other words, that we should reduce them
all to the same genus. The various objects, for example, animate and inanimate, which are, at this moment before me, I may
class and number in a variety of different ways, according to the
view of them that I choose to take. I may reckon successively
the number of sheep, of cows, of horses, of elms, of oaks, of
beeches; or I may first reckon the number of animals, and then
the number of trees; or I may first reckon the number of all
the organized substances which my senses present to me. But
whatever be the principle on which my classification proceeds,
it is evident that the objects numbered together must be considered in those respects only in which they agree with each other;
and that, if I had no power of separating the combinations of
sense, I never could have conceived them as forming a plurality.
This power of considering certain qualities or attributes of an
object apart from the rest; or, as I would rather choose to define
it, the power which the understanding has of separating the combinations which are presented to it, is distinguished by logicians