9. This judgment apt to be mistaken for direct perception.
But this is not, I think, usual in any of our ideas, but
those received by sight. Because sight, the most comprehensive of all our senses, conveying to our minds the
ideas of light and colours, which are peculiar only to that sense; and also the far different ideas of space, figure,
and motion, the several varieties whereof change the appearances of its proper object, viz., light and colours; we
bring ourselves by use to judge of the one by the other. This, in many cases by a settled habit,--in things whereof
we have frequent experience, is performed so constantly and so quick, that we take that for the perception of our
sensation which is an idea formed by our judgment; so that one, viz., that of sensation, serves only to excite the
other, and is scarce taken notice of itself;--as a man who reads or hears with attention and understanding, takes
little notice of the characters or sounds, but of the ideas that are excited in him by them.
