"
There is no doubt that he who has not studied any works on mental philosophy,
who has not comprehended the nature of the mind, who has no knowledge of its
essence, and considers it in no other way than he would consider the nature of
whiteness and blackness, will find this subject extremely difficult. Even
amongst those who imagine that they are wise, many find this subject
difficult, and are of opinion that it is impossible for the mind of this
proposition, although it is a demonstrated truth, as has been shown by
metaphysicians.

I will tell you now what has been proved. Man, before comprehending a thing,
comprehends it in potentia; when, however, he comprehends a thing, e.g. the
form of a certain tree which is pointed out to him, when he abstracts its form
from its substance, and reproduces the abstract form, an act performed by the
intellect, he comprehends in reality, and the intellect which he has acquired
in actuality, is the abstract form of the tree in man's mind.

For in such a case the intellect is not a thing distinct from the thing
comprehended. It is therefore clear to you that the thing comprehended is the
abstract form of the tree, and at the same time it is the intellect in action;
and that the intellect and the abstract form of the tree are not two different
things, for the intellect in action is nothing but the thing comprehended, and
that agent by which the form of the tree has been turned into an intellectual
and abstract object, namely, that which comprehends, is undoubtedly the
intellect in action.

All intellect is identical with its action - the intellect in action is not a
thing different from its action, for the true nature and assence of the
intellect is comprehension, and you must not think that the intellect in
action is a thing existing by itself, separate from comprehension, and that
comprehension is a different thing connected with it; for the very essence of
the intellect is comprehension. In assuming an intellect in action you assume
the comprehension of the thing comprehended. This is quite clear to all who
have made themselves familiar with the figurative language common to this
discipline.

You therefore accept it as proved that the intellect consists in its action,
which is its true nature and essence. Consequently the very thing by which the
form of that tree has been made abstract and intelligible, viz., the
intellect, is at the same time the intelligens, for the intellect is itself
the agens which abstracts the form and comprehends it, and that is the action,
on account of which it is called the intelligens - but itself and its action
are identical - and that which is called intellect in action consists [in the
above mentioned instance] of nothing else but the form of the tree.

It must now be obvious to you that whenever the intellect is found in action,
the intellect and the thing comprehended are one and the same thing - and also
that the function of all intellect, namely, the act of comprehending, is its
essence. The intellect, that which comprehends and that which is comprehended,
are therefore the same, whenever a real comprehension takes place.

But when, we speak of the power of comprehension, we necessarily distinguish
two things: the power itself, and the thing which can be comprehended - e.g.
that hylic intellect of Zaid is the power of comprehension, and this tree is,
in like manner, a thing which is capable of being comprehended - these,
undoubtedly, are two different things. When, however, the potential is
replaced by the actual, and when the form of the tree has really been
comprehended, the form comprehended is the intellect, and it is by that same
intellect, by the intellect in action, that the tree has been converted into
an abstract idea, and has been comprehended. For everything in which a real
action takes place exists in reality.

On the other hand, the power of comprehension, and the object capable of
comprehension are two things - but that which is only potential cannot be
imagined otherwise than in connexion with an object possessing that capacity,
as, e.g. man, and thus we have three things: the man who possesses the power,
and is capable of comprehending - that power itself, namely, the power of
comprehension, and the object which presents itself as an object of
comprehension, and is capable of being comprehended - to use the foregoing
example, the man, the hylic intellect, and the abstract form of the tree, are
three different things. They become one and the same thing when the intellect
is in action, and you will never find the intellect different from
comprehensible object, unless the power of comprehending and the power of
being comprehended be referred to.

"
-Rambam, 12nd century thinker

... not bad for a 12nd century 'caveman'