3p19d.md (829B)
1 The mind, as far as possible, endeavours to conceive 2 those things which increase or help the body's power of activity 3 (III. xii.); in other words (III. xii. note), those things which 4 it loves. But conception is helped by those things which 5 postulate the existence of a thing, and contrariwise is hindered 6 by those which exclude the existence of a thing (II. xvii.); 7 therefore the images of things, which postulate the existence of 8 an object of love, help the mind's endeavour to conceive the 9 object of love, in other words (III. xi. note), affect the mind 10 pleasurably; contrariwise those things, which exclude the 11 existence of an object of love, hinder the aforesaid mental 12 endeavour; in other words, affect the mind painfully. He, 13 therefore, who conceives that the object of his love is destroyed 14 will feel pain, &c. Q.E.D. 15 16