A Treatise of Human Nature | Page 7

to any impressions, are
obstructed in their operations, as when one is born blind or deaf; not only the impressions
are lost, but also their correspondent ideas; so that there never appear in the mind the
least traces of either of them. Nor is this only true, where the organs of sensation are
entirely destroyed, but likewise where they have never been put in action to produce a
particular impression. We cannot form to ourselves a just idea of the taste of a pine apple,
without having actually tasted it.
There is however one contradictory phaenomenon, which may prove, that it is not
absolutely impossible for ideas to go before their correspondent impressions. I believe it
will readily be allowed that the several distinct ideas of colours, which enter by the eyes,
or those of sounds, which are conveyed by the hearing, are really different from each
other, though at the same time resembling. Now if this be true of different colours, it

must be no less so of the different shades of the same colour, that each of them produces
a distinct idea, independent of the rest. For if this should be denied, it is possible, by the
continual gradation of shades, to run a colour insensibly into what is most remote from it;
and if you will not allow any of the means to be different, you cannot without absurdity
deny the extremes to be the same. Suppose therefore a person to have enjoyed his sight
for thirty years, and to have become perfectly well acquainted with colours of all kinds,
excepting one particular shade of blue, for instance, which it never has been his fortune to
meet with. Let all the different shades of that colour, except that single one, be placed
before him, descending gradually from the deepest to the lightest; it is plain, that he will
perceive a blank, where that shade is wanting, said will be sensible, that there is a greater
distance in that place betwixt the contiguous colours, than in any other. Now I ask,
whether it is possible for him, from his own imagination, to supply this deficiency, and
raise up to himself the idea of that particular shade, though it had never been conveyed to
him by his senses? I believe i here are few but will be of opinion that he can; and this
may serve as a proof, that the simple ideas are not always derived from the correspondent
impressions; though the instance is so particular and singular, that it is scarce worth our
observing, and does not merit that for it alone we should alter our general maxim.
But besides this exception, it may not be amiss to remark on this head, that the principle
of the priority of impressions to ideas must be understood with another limitation, viz.,
that as our ideas are images of our impressions, so we can form secondary ideas, which
are images of the primary; as appears from this very reasoning concerning them. This is
not, properly speaking, an exception to the rule so much as an explanation of it. Ideas
produce the images of them. selves in new ideas; but as the first ideas are supposed to be
derived from impressions, it still remains true, that all our simple ideas proceed either
mediately or immediately, from their correspondent impressions.
This then is the first principle I establish in the science of human nature; nor ought we to
despise it because of the simplicity of its appearance. For it is remarkable, that the present
question concerning the precedency of our impressions or ideas, is the same with what
has made so much noise in other terms, when it has been disputed whether there be any
INNATE IDEAS, or whether all ideas be derived from sensation and reflexion. We may
observe, that in order to prove the ideas of extension and colour not to be innate,
philosophers do nothing but shew that they are conveyed by our senses. To prove the
ideas of passion and desire not to be innate, they observe that we have a preceding
experience of these emotions in ourselves. Now if we carefully examine these arguments,
we shall find that they prove nothing but that ideas are preceded by other more lively
perceptions, from which the are derived, and which they represent. I hope this clear
stating of the question will remove all disputes concerning it, and win render this
principle of more use in our reasonings, than it seems hitherto to have been.

SECT. II. DIVISION OF THE SUBJECT.
Since it appears, that our simple impressions are prior to their correspondent ideas, and
that the exceptions are very rare, method seems to require we should examine our
impressions, before we consider our ideas. Impressions way be divided into