Argument: Animals feel and suffer in very similar ways as humans
Voltaire, Traité sur la tolerance - "People must have renounced, it seems to me, all natural intelligence to dare to advance that animals are but animated machines.... It appears to me, besides, that [such people] can never have observed with attention the character of animals, not to have distinguished among them the different voices of need, of suffering, of joy, of pain, of love, of anger, and of all their affections. It would be very strange that they should express so well what they could not feel."
Ingrid Newkirk - "When it comes to having a central nervous system, and the ability to feel pain, hunger, and thirst, a rat is a pig is a dog is a boy."
Buddha - "All beings tremble before violence. All fear death, all love life. See yourself in others. Then whom can you hurt? What harm can you do?"
Peter Singer, Australian Animal Activist - "The animal liberation movement is saying that where animals and humans have similar interests - we might take the interest in avoiding physical pain as an example, for it is an interest that humans clearly share with other animals - those interests are to be counted equally, with no automatic discount just because one of the beings is not human."
Thomas Chalmers, Scottish Religious Leader - "The brute animals have all the same sensations of pain as human beings, and consequently endure as much pain when their body is hurt; but in their case the cruelty of torment is greater, because they have no mind to bear them up against their sufferings, and no hope to look forward to when enduring the last extreme pain..."