Mount Everest, for, equally in both cases, the ideas are copies of
sensible impressions, although of complex, not simple, ones--of colour
and graduation in the first case, of size and increase in the second.
Still, there is at least one genuine exception, which it is the more
remarkable that Hume should have overlooked, as it may be said to have
stared him in the face from the very subject-matter he was considering.
Our idea of idea itself, from what sensible impression is that derived?
We have just been told that the difference between an idea and a
sensation is that the first is a copy of the second, a feeble copy of a
lively original. The idea therefore is not itself a sensation; the copy
is not itself an original. Neither consequently can the idea or notion
which the mind proceeds to form of any of its previous ideas be derived
from or be a copy of a sensation: it cannot have entered the mind 'in
the only manner by which,' according to Hume, 'an idea can have access
to the mind, to wit, by actual feeling and sensation.'

Let me not be misunderstood. Let me not be supposed to be courting
collision with the Berkleian thesis of the non-existence of abstract
ideas. I do not for one moment doubt that all our general or class
notions of sensible objects or events are merely concrete ideas of
individual objects or events--that, for instance, whenever we talk of
man or motion in general, we are really thinking of some particular man
or motion, which, as possessing all properties common to all men or
motions, serves as a representative of the entire _genus_. Neither am I
prepared to deny, although scarcely either prepared to admit, that even
of abstract qualities all our general or class notions are equally ideas
of particular specimens of those qualities; that, when we speak, for
instance, of virtue or vice in general, we are thinking of some
particular exhibition of some particular kind of virtue or vice. Nay, I
am not even concerned to deny that our idea of idea in general may
possibly be a copy of some particular one of our previous ideas which,
for the nonce, serves to represent all our other previous ideas. I limit
myself to saying that our idea of idea in general, whether it be or be
not itself an abstraction, is, at all events, not a copy of sensation. I
admit that it thereby differs essentially from most, if not all, other
general ideas. Possibly it may be only through my having myself felt
the promptings of some p