Propositions 12 to 14

12. As far as it can, the mind endeavours to conceive things which increases or helps the power of activity in the body.

Proof: So long as the human body is affected in a mode, which involves the nature of any external body, the human mind will regard that external body as present (2.17).

Consequently (2.7), so long as the human mind regards an external body as present, that is (2.17. note), conceives it, the human body is affected in a mode, which involves the nature of the said external body.

Thus, so long as the mind conceives things, which increase or help the power of activity in our body, the body is affected in modes which increase or help its power of activity (3. Post. 1).

Consequently, (3.11) the mind’s power of thinking is for that period increased or helped.

Thus (3.6., 3.9) the mind, as far as it can, endeavours to imagine such things. Q.E.D.

13. When the mind conceives things which reduce or hinder the body’s power of activity, it endeavours, as far as possible, to remember things which exclude the existence of the first-named things.

Proof: So long as the mind conceives anything of the kind alluded to, the power of the mind and body is reducedc or constrained (cf. 3. 12. Proof).

Nevertheless, it will continue to conceive it, until the mind conceives something else, which excludes the present existence thereof (2.17).

That is, the power of the mind and of the body is reduced or constrained, until the mind conceives something else, which excludes the existence of the former thing conceived.

Therefore, the mind (3.9), as far as it can, will endeavour to conceive or remember the latter. Q.E.D. –>

Corollary: It follows that the mind shrinks from conceiving those things, which reduce or constrain the power of itself and of the body.

Note: This explains the nature of Love and Hate.

Love is pleasure accompanied by the idea of an external cause.

Hate is pain accompanied by the idea of an external cause.

He who loves necessarily endeavours to have, and to keep present to him, the object of his love.

While he who hates endeavours to remove and destroy the object of his hatred.

But I will treat of these matters at more length hereafter. –>

14. If the mind has once been affected by two emotions at the same time, it will, whenever it is afterwards affected by one of these two, be also affected by the other.

Proof: If the human body has once been affected by two bodies at once, whenever afterwards the mind conceives one of them, it will straightway remember the other also (2.18).

But the mind’s conceptions indicate rather the emotions of our body than the nature of external bodies (2.16. Coroll. 2).

Therefore, if the body, and consequently the mind (3. Def. 3) has been once affected by two emotions at the same time, it will, whenever it is afterwards affected by one of the two, be also affected by the other.