Just as nobody pursues happiness in order to find anything other than happiness, so nobody strives to reduce pain to reduce anything other than pain.… - Richard D. Ryder

Differences in reaction to toxic substances vary considerably between species so that the value of these tests remains doubtful. Although thalidomide was extensively tested on animals in several countries, its terrible properties were not discovered. Conversely, penicillin, the greatest medical discovery of the century, was not extensively tested on animals before its miraculous therapeutic qualities were demonstrated in human patients. If it had been fully tested on animals its high toxicity for guinea pigs would have almost certainly prevented its clinical use.

Their experiences may be more simple than ours, but are they less intense? Perhaps a caterpillar’s primitive pain when squashed is greater than our more sophisticated sufferings.

It is always wrong to cause pain to A merely in order to increase the pleasure of B.