Selection from – Ethics – Part IV. Of Human Bondage, or the Strength of the Emotions (Page 7)

Spinoza's Words: (reason makes no demands contrary to nature)

In [the prevous] remarks I have explained the causes of human infirmity and inconstancy, and shown why men do not abide by the precepts of reason. It now remains for me to show what course is marked out for us by reason, which of the emotions are in harmony with the rules of human reason, and which of them are contrary thereto. But, before I begin to prove my Propositions in detailed geometrical fashion, it is advisable to sketch them briefly in advance, so that everyone may more readily grasp my meaning.

As reason makes no demands contrary to nature, it demands, that every man should love himself, should seek that which is useful to him—I mean, that which is really useful to him, should desire everything which really brings man to greater perfection, and should, each for himself, endeavour as far as he can to preserve his own being. This is as necessarily true, as that a whole is greater than its part.

Again, as virtue is nothing else but action in accordance with the laws of one's own nature, it follows, first, that the foundation of virtue is the endeavour to preserve one's own being, and that happiness consists in man's power of preserving his own being; secondly, that virtue is to be desired for its own sake, and that there is nothing more excellent or more useful to us, for the sake of which we should desire it; thirdly and lastly, that suicides are weak-minded, and are overcome by external causes repugnant to their nature.

Further, we can never arrive at doing without all external things for the preservation of our being or living, so as to have no relations with things which are outside ourselves... There are, then, many things outside ourselves, which are useful to us, and are, therefore, to be desired. Of such none can be discerned more excellent, than those which are in entire agreement with our nature. For if, for example, two individuals of entirely the same nature are united, they form a combination twice as powerful as either of them singly.