_The theory of Pleasure and Pain_.

The Stoics agreed with the Peripatetics (anterior to Epicurus, not specially against _him_) that the first principle of nature is (not pleasure or relief from pain, but) _self-preservation_ or _self-love_; in other words, the natural appetite or tendency of all creatures is, to preserve their existing condition with its inherent capacities, and to keep clear of destruction or disablement.

This appetite (they said) manifests itself in little children before any pleasure or pain is felt, and is moreover a fundamental postulate, pre-supposed in all desires of particular pleasures, as well as in all aversions to particular pains.

We begin by loving our own vitality; and we come, by association, to love what promotes or strengthens our vitality; we hate destruction or disablement, and come (by secondary association) to hate whatever produces that effect.[8] The doctrine here laid down associated, and brought under one view, what was common to man, not merely with the animal, but also with the vegetable world; a plant was declared to have an impulse or tendency to maintain itself, even without feeling pain or pleasure.

Aristotle (in the tenth Book of the Ethics) says, that he will not determine whether we love life for the sake of pleasure, or pleasure for the sake of life; for he affirms the two to be essentially yoked together and inseparable; pleasure is the consummation of our vital manifestations.