PROP. XXXII. If we conceive that anyone takes delight in something, which only one person can possess, we shall endeavour to bring it about that the man in question shall not gain possession thereof.

Proof.—From the mere fact of our conceiving that another person takes delight in a thing (III. xxvii. and Coroll.) we shall ourselves love that thing and desire to take delight therein. But we assumed that the pleasure in question would be prevented by another's delight in its object; we shall, therefore, endeavour to prevent his possession thereof (III. xxviii.). Q.E.D.

Note.—We thus see that man's nature is generally so constituted, that he takes pity on those who fare ill, and envies those who fare well with an amount of hatred proportioned to his own love for the goods in their possession. Further, we see that from the same property of human nature, whence it follows that men are merciful, it follows also that they are envious and ambitious. Lastly, if we make appeal to Experience, we shall find that she entirely confirms what we have said; more especially if we turn our attention to the first years of our life. We find that children, whose body is continually, as it were, in equilibrium, laugh or cry simply because they see others laughing or crying; moreover, they desire forthwith to imitate whatever they see others doing, and to possess themselves of whatever they conceive as delighting others: inasmuch as the images of things are, as we have said, modifications of the human body, or modes wherein the human body is affected and disposed by external causes to act in this or that manner.

PROP. XXXIII. When we love a thing similar to ourselves we endeavour, as far as we can, to bring about that it should love us in return.

Proof.—That which we love we endeavour, as far as we can, to conceive in preference to anything else (III. xii.). If the thing be similar to ourselves, we shall endeavour to affect it pleasurably in preference to anything else (III. xxix.). In other words, we shall endeavour, as far as we can, to bring it about, that the thing should be affected with pleasure accompanied by the idea of ourselves, that is (III. xiii. note), that it should love us in return. Q.E.D.

PROP. XXXIV. The greater the emotion with which we conceive a loved object to be affected towards us, the greater will be our complacency.

Proof.—We endeavour (III. xxxiii.), as far as we can, to bring about, that what we love should love us in return: in other words, that what we love should be affected with pleasure accompanied by the idea of ourself as cause. Therefore, in proportion as the loved object is more pleasurably affected because of us, our endeavour will be assisted.—that is (III. xi. and note) the greater will be our pleasure. But when we take pleasure in the fact, that we pleasurably affect something similar to ourselves, we regard ourselves with pleasure (III. 30); therefore the greater the emotion with which we conceive a loved object to be affected, &c. Q.E.D.

PROP. XXXV. If anyone conceives, that an object of his love joins itself to another with closer bonds of friendship than he himself has attained to, he will be affected with hatred towards the loved object and with envy towards his rival.

Proof.—In proportion as a man thinks, that a loved object is well affected towards him, will be the strength of his self—approval (by the last Prop.), that is (III. xxx. note), of his pleasure; he will, therefore (III. xxviii.), endeavour, as far as he can, to imagine the loved object as most closely bound to him: this endeavour or desire will be increased, if he thinks that someone else has a similar desire (III. xxxi.). But this endeavour or desire is assumed to be checked by the image of the loved object in conjunction with the image of him whom the loved object has joined to itself; therefore (III. xi. note) he will for that reason be affected with pain, accompanied by the idea of the loved object as a cause in conjunction with the image of his rival; that is, he will be (III. xiii.) affected with hatred towards the loved object and also towards his rival (III. xv. Coroll.), which latter he will envy as enjoying the beloved object. Q.E.D.

Note.—This hatred towards an object of love joined with envy is called Jealousy, which accordingly is nothing else but a wavering of the disposition arising from combined love and hatred, accompanied by the idea of some rival who is envied. Further, this hatred towards the object of love will be greater, in proportion to the pleasure which the jealous man had been wont to derive from the reciprocated love of the said object; and also in proportion to the feelings he had previously entertained towards his rival. If he had hated him, he will forthwith hate the object of his love, because he conceives it is pleasurably affected by one whom he himself hates: and also because he is compelled to associate the image of his loved one with the image of him whom he hates. This condition generally comes into play in the case of love for a woman: for he who thinks, that a woman whom he loves prostitutes herself to another, will feel pain, not only because his own desire is restrained, but also because, being compelled to associate the image of her he loves with the parts of shame and the excreta of another, he therefore shrinks from her.