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or species entirely different from the ideas of touch: nor will any man,
I presume, say they can make themselves perceived by that sense: but
there is no other immediate object of sight besides light and colours. It
is therefore a direct consequence that there is no idea common to both
senses.

130. It is a prevailing opinion, even amongst those who have thought and
writ most accurately concerning our ideas and the ways whereby they enter
into the understanding, that something more is perceived by sight than
barely light and colours with their variations. Mr. Locke termeth 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. ESSAY ON HUMAN
UNDERSTAND. B. ii. C. 9. S. 9. Space or distance, we have shown, is not
otherwise the object of sight than of hearing. VID. sect. 46. And as for
figure and extension, I leave it to anyone that shall calmly attend to
his own clear and distinct ideas to decide whether he had any idea
intromitted immediately and properly by sight save only light and
colours: or whether it De possible for him to frame in his mind a
distinct abstract idea of visible extension or figure exclusive of all
colour: and on the other hand, whether he can conceive colour without
visible extension? For my own part, I must confess I am not able to
attain so great a nicety of abstraction: in a strict sense, I see nothing
but light and colours, with their several shades and variations. He who
beside these doth also perceive by sight ideas far different and distinct
from them hath that faculty in a degree more perfect and comprehensive
than I can pretend to. It must be owned that by the mediation of light
and colours other far different ideas are suggested to my mind: but so
they are by hearing, which beside sounds which are peculiar to that
sense, doth by their mediation suggest not only space, figure, and
motion, but also all other ideas whatsoever that can be signified by
words.

131. THIRDLY, it is, I think, an axiom universally received that
quantities of the same kind may be added together and make one entire
sum. Mathematicians add lines together: but they do not add a line to a
solid, or conceive it as making one sum with a surface: these three kinds
of quantity being thought incapable of any such mutual addition, and
consequently of being compared