Y: I suppose you also deem it a crime to drink, as you destroy myriads of animals in the water of every draught? Z: I consider this an evil, but not … - Lewis Gompertz

It is an axiom that the more pleasure and the less pain there is in the Universe, the better it is. If, then, a person suffer pain instead of pleasure, whether he be criminal or not, the pain will be increased and the pleasure decreased; and, as this disagrees with the axiom just cited, it is wrong.

The slaying of animals for the most trifling purposes is defended on the ground, that if not done, they would be too numerous, and consequently troublesome to man, and unhappy in themselves; while the promotion of their increase is defended on the assumption, that we are then the authors of much happiness. But let us apply a cautious ear to such reasoning. If the promoting the increase of animals is being the author of increased happiness, destroying them must be positive evil. For our own parts, we prefer neutrality as much as possible on these points, because we know not whether the life of animals generally, abound most with pleasure or pain. We confess that in our view of the question, pain seems to predominate; and the more so the more the numbers of animals are increased; indeed, we neither approve the promoting of the increase of animals, nor of destroying them.

Y: Do you include those animals which are guilty of the same crime themselves by living on prey? Should we not then save a thousand lives by killing one?
Z: We must never suppose a person or an animal guilty until they are found in the act, and then we must investigate the nature of the crime. It is true that the animal living by slaughter may be less entitled to our consideration than the animal which is harmless; but recollect, the former may plead the same excuse itself, unless his slaughter be only of those animals which live on vegetables; and then, though justice may require their destruction, it would be repugnant to the feelings of humanity to slaughter them with that plea, unless we could quite assure our conscience that our design in killing them was more to prevent their doing mischief than for our own benefit: besides, we might then extend this principle still further, and kill our own species because they are also animals of prey. It is moreover to be observed, that if one carnivorous animal kills another, he may save lives by it also, and the nature of the act will be different according to circumstances [...] And, further, it will frequently be impossible to discover when the animal becomes guilty or innocent, as it depends on such a variety of circumstances: we should therefore be more safe from infringing the laws of moral rectitude, not to interfere in this case.