ave said above (A. 3).
Secondly, the indivisible is so called in relation to species, as
man's reason is something indivisible. This way, also, the
indivisible is understood before its division into logical parts, as
we have said above (De Anima iii, 6); and again before the intellect
disposes and divides by affirmation and negation. The reason of this
is that both these kinds of indivisible are understood by the
intellect of itself, as being its proper object. The third kind of
indivisible is what is altogether indivisible, as a point and unity,
which cannot be divided either actually or potentially. And this
indivisible is known secondarily, through the privation of
divisibility. Wherefore a point is defined by way of privation "as
that which has no parts"; and in like manner the notion of "one" is
that is "indivisible," as stated in _Metaph._ x, Did. ix, 1. And the
reason of this is that this indivisible has a certain opposition to
a corporeal being, the quiddity of which is the primary and proper
object of the intellect.

But if our intellect understood by participation of certain separate
indivisible (forms), as the Platonists maintained, it would follow
that a like indivisible is understood primarily; for according to
the Platonists what is first is first participated by things.

Reply Obj. 1: In the acquisition of knowledge, principles and
elements are not always (known) first: for sometimes from sensible
effects we arrive at the knowledge of principles and intelligible
causes. But in perfect knowledge, the knowledge of effects always
depends on the knowledge of principles and elements: for as the
Philosopher says in the same passage: "Then do we consider that we
know, when we can resolve principles into their causes."

Reply Obj. 2: A point is not included in the definition of a line in
general: for it is manifest that in a line of indefinite length, and
in a circular line, there is no point, save potentially. Euclid
defines a finite straight line: and therefore he mentions a point in
the definition, as the limit in the definition of that which is
limited. Unity is the measure of number: wherefore it is included in
the definition of a measured number. But it is not included in the
definition of the divisible, but rather conversely.

Reply Obj. 3: The likeness through which we understand is the species
of the known in the knower; therefore a thing is known first, not on
account of its natural likeness to the