2p49d.md (1301B)
1 There is in the mind no absolute faculty of positive 2 or negative volition, but only particular volitions, namely, this 3 or that affirmation, and this or that negation. Now let us 4 conceive a particular volition, namely, the mode of thinking 5 whereby the mind affirms, that the three interior angles of a 6 triangle are equal to two right angles. This affirmation 7 involves the conception or idea of a triangle, that is, without 8 the idea of a triangle it cannot be conceived. It is the same 9 thing to say, that the concept A must involve the concept B, as 10 it is to say, that A cannot be conceived without B. Further, 11 this affirmation cannot be made (II. Ax. iii.) without the idea 12 of a triangle. Therefore, this affirmation can neither be nor be 13 conceived, without the idea of a triangle. Again, this idea of a 14 triangle must involve this same affirmation, namely, that its 15 three interior angles are equal to two right angles. Wherefore, 16 and vice versâ, this idea of a triangle can neither be nor be 17 conceived without this affirmation, therefore, this affirmation 18 belongs to the essence of the idea of a triangle, and is nothing 19 besides. What we have said of this volition (inasmuch as we have 20 selected it at random) may be said of any other volition, namely, 21 that it is nothing but an idea. Q.E.D. 22 23