Selection from – Ethics – Part III. On the Nature and Origin of the Emotions (Page 22)

Spinoza's Words: (on love and hate)

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

Explanation—This definition explains sufficiently clearly the essence of love; the definition given by those authors who say that love is the lover's wish to unite himself to the loved object expresses a property, but not the essence of love; and, as such authors have not sufficiently discerned love's essence, they have been unable to acquire a true conception of its properties, accordingly their definition is on all hands admitted to be very obscure.

It must, however, be noted, that when I say that it is a property of love, that the lover should wish to unite himself to the beloved object, I do not here mean by wish consent, or a free decision of the mind; neither do I mean a desire of being united to the loved object when it is absent, or of continuing in its presence when it is at hand; for love can be conceived without either of these desires; but by wish I mean the contentment, which is in the lover, on account of the presence of the beloved object, whereby the pleasure of the lover is strengthened, or at least maintained.

VII. Hatred is pain, accompanied by the idea of an external cause