This compassion, or sympathy with the pains of others, ought also to extend to the brute creation, as far as our necessities will admit; for we cannot exist long without the destruction of other animal or vegetable beings either in their mature or embryon state. Such is the condition of mortality, that the first law of nature is 'eat, or be eaten.' Hence for the preservation of our existence we may be supposed to have a natural right to kill those brute creatures, which we want to eat, or which want to eat us; but to destroy even insects wantonly shows an unreflecting mind, or a depraved heart.
Erasmus Darwin, A Plan for the Conduct of Female Education, in Boarding Schools
law, nature