“It happens then,” he continued, “with respect to some of such things,
that not only is the idea itself always thought worthy of the same
appellation, but likewise something else which is not indeed that idea
itself but constantly retains its form so long as it exists. What I mean
will perhaps be clearer in the following examples. The odd in number
must always possess the name by which we now call it; must it not?”
“Certainly.”
“Must it alone of all things, for this I ask, or is there any thing
else, which is not the same as the odd, but yet which we must always
call odd, together with its own name, because it is so constituted by
nature, that it can never be without the odd? But this I say is the case
with the number three, and many others. For consider with respect to the
number three; does it not appear to you that it must always be called by
its own name, as well as by that of the odd, which is not the same as
the number three? Yet such is the nature of the number three, five, and
the entire half of number, that though they are not the same as the odd,
yet each of them is always odd. And again, two and four, and the whole
other series of number, though not the same as the even, are
nevertheless each of them always even: do you admit this or not?”