The Island of Dr. Moreau
"But," said I, "I still do not understand. Where is your justification for inflicting all this pain? The only thing that could excuse vivisection to me would be some application—"
"Precisely," said [Moreau]. "But you see I am differently constituted. We are on different platforms. You are a materialist." (14.18-19)
"To this day I have never troubled about the ethics of the matter. The study of Nature makes a man at last as remorseless as Nature." (14.29)
"We can't massacre the lot,—can we? I suppose that's what your humanity would suggest?… But they'll change. They are sure to change." (19.6)