nse-perception must always be
somewhat surprising to an inquirer who is used to transcendental
reflection, and is thereby rendered cautious. It leads us to feel some
misgiving as to whether the understanding can anticipate such a
synthetic proposition as that respecting the degree of all that is
real in phenomena, and consequently respecting the possibility of the
internal distinction of sensation itself, if we abstract from its
empirical quality. There remains, therefore, a problem not unworthy of
solution, viz. 'How can the understanding pronounce synthetically and
_a priori_ upon phenomena in this respect, and thus anticipate
phenomena even in that which is specially and merely empirical, viz.
that which concerns sensations?'"[12] But although Kant recognizes
that the anticipation is surprising, he is not led to revise his
general theory, as being inconsistent with the existence of the
anticipation. He indeed makes an attempt[13] to deal with the
difficulty; but his solution consists not in showing that the
anticipation is consistent with his general theory--as he should have
done, if the theory was to be retained--but in showing that, in the
case of the degree of sensation, we do apprehend the nature of
sensation _a priori_.

[12] B. 217, M. 131; cf. B. 209, M. 127.

[13] B. 217-18, M. 132.

Strangely enough, Hume finds himself face to face with what is in
principle the same difficulty, and treats it in a not dissimilar way.
"There is, however, one contradictory phenomenon, which may prove,
that 'tis not absolutely impossible for ideas to go before their
correspondent impressions. I believe it will readily be allow'd, that
the several distinct ideas of colours, which enter by the eyes, or
those of sounds, which are convey'd by the hearing, are really
different from each other, tho' 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 shou'd be deny'd,
'tis 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 part