extremity? And in like manner does the touch adequately perceive the
qualities of thickness or thinness, of softness or hardness? And so of
the other senses; do they give perfect intimations of such matters? Is
not their mode of operation on this wise--the sense which is concerned
with the quality of hardness is necessarily concerned also with the
quality of softness, and only intimates to the soul that the same thing
is felt to be both hard and soft?

You are quite right, he said.

And must not the soul be perplexed at this intimation which the sense
gives of a hard which is also soft? What, again, is the meaning of
light and heavy, if that which is light is also heavy, and that which is
heavy, light?

Yes, he said, these intimations which the soul receives are very curious
and require to be explained.

Yes, I said, and in these perplexities the soul naturally summons to her
aid calculation and intelligence, that she may see whether the several
objects announced to her are one or two.

True.

And if they turn out to be two, is not each of them one and different?

Certainly.

And if each is one, and both are two, she will conceive the two as in
a state of division, for if there were undivided they could only be
conceived of as one?

True.

The eye certainly did see both small and great, but only in a confused
manner; they were not distinguished.

Yes.

Whereas the thinking mind, intending to light up the chaos, was
compelled to reverse the process, and look at small and great as
separate and not confused.

Very true.

Was not this the beginning of the enquiry 'What is great?' and 'What is
small?'

Exactly so.

And thus arose the distinction of the visible and the intelligible.

Most true.

This was what I meant when I spoke of impressions which invited the
intellect, or the reverse--those which are simultaneous with opposite
impressions, invite thought; those which are not simultaneous do not.

I understand, he said, and agree with you.

And to which class do unity and number belong?

I do not know, he replied.

Think a little and you will see that what has preceded will supply the
answer; for if simple unity could be adequately perceived by the sight
or by any other sense, then, as we were saying in the case of the
finger, there would be nothing to attract towards being; but when there
is some contradiction always present, and one is the reverse of one and
involves the conception of plur