"I may begin by laying down as a principle that ‘all pain of human or rational beings is to be avoided’; and then afterwards may be led to enunciate the wider rule that ‘all pain is to be avoided’; it being made evident to me that the difference of rationality between two species of sentient beings is no ground for establishing a fundamental ethical distinction between their respective pains."

“Now, I agree with Mill in holding that the scientific study of the structures and functions of the different governments that have actually existed in human societies cannot well be pursued in complete separation from the scientific study of other important elements of the societies in question : whether the aim of the student is to ascertain the causes of the differences in such governments or to examine their effects. But I do not think that there is any fundamental difference, in this respect, between the study of political relations and the study of economic relations, or, again, of religion, of art, of science and philosophy, as factors of social life. In each of these eases the student concentrates his attention on one element of human history which can only be partially separated from other components of the whole complex fact of social development. Experience seems to show that this kind of concentration, and consequent partial separation of historical and sociological study into special branches, is unavoidable in the division of intellectual labour which the growth of our knowledge renders necessary in a continually increasing degree.”

“For philosophy and history alike have taught...to seek not what is "safe," but what is true.”

“The good of any one individual is of no more importance, from the point of view of the Universe, than the good of any other; unless, that is, there are special grounds for believing that more good is likely to be realized in the one case than in the other.”

“Henry Sidgwick, biographical profile, including quotes and further resources in Introduction to Utilitarianism: An Online Textbook”