Another type of ultimate disagreement between utilitarians, whether hedonistic or ideal, can arise over whether we should try to maximize the average… - J. J. C. Smart

The reason why there are hardly ever completely knock-down arguments, except between very like minded philosophers, is that philosophers, unlike chemists or geologists, are licensed to question everything, including methodology.

I regard Peter as one of the great moralists, because I suspect that more than anyone he has helped to change the attitudes of very many people to the sufferings of animals. Peter is a utilitarian in normative ethics, and a humane attitude to animals is a natural corollary of utilitarianism. Utilitarian concern for animals goes back to Bentham, who, presumably alluding to the Kantians, said that the question was not whether animals can reason, but whether they can suffer.

The utilitarian’s ultimate moral principle...expresses the sentiment not of altruism but of benevolence, the agent counting himself neither more nor less than any other person. Pure altruism cannot be made the basis of a universal moral discussion because it might lead different people to different and perhaps incompatible courses of action, even though the circumstances were identical. When two men each try to let the other through a door first a deadlock results...Of course we often tend to praise and honour altruism even more than generalized benevolence. This is because people too often err on the side of selfishness, and so altruism is a fault on the right side. If we can make a man try to be an altruist he may succeed as far as acquiring a generalized benevolence.