Benedict de Spinoza, THE ETHICS
Page: 41

further, I would here remark that, by the will to affirm and
decide, I mean the faculty, not the desire. I mean, I repeat,
the faculty, whereby the mind affirms or denies what is true or
false, not the desire, wherewith the mind wishes for or turns
away from any given thing. After we have proved, that these
faculties of ours are general notions, which cannot be
distinguished from the particular instances on which they are
based, we must inquire whether volitions themselves are anything
besides the ideas of things. We must inquire, I say, whether
there is in the mind any affirmation or negation beyond that,
which the idea, in so far as it is an idea, involves. On which
subject see the following proposition, and II. Def. iii., lest
the idea of pictures should suggest itself. For by ideas I do
not mean images such as are formed at the back of the eye, or in
the midst of the brain, but the conceptions of thought.

XLIX. There is in the mind no volition or affirmation and
negation, save that which an idea, inasmuch as it is an idea,
involves.

>>>>>Proof--There is in the mind no absolute faculty of positive
or negative volition, but only particular volitions, namely,
this or that affirmation, and this or that negation. Now let us
conceive a particular volition, namely, the mode of thinking
whereby the mind affirms, that the three interior angles of a
triangle are equal to two right angles. This affirmation
involves the conception or idea of a triangle, that is, without
the idea of a triangle it cannot be conceived. It is the same
thing to say, that the concept A must involve the concept B, as
it is to say, that A cannot be conceived without B. Further,
this affirmation cannot be made (II. Ax. iii.) without the idea
of a triangle. Therefore, this affirmation can neither be nor
be conceived, without the idea of a triangle. Again, this idea
of a triangle must involve this same affirmation, namely, that
its three interior angles are equal to two right angles.
Wherefore, and vice versa, this idea of a triangle can neither be
nor be conceived without this affirmation, therefore, this