Were we incapable of empathy – of putting ourselves in the position of others and seeing that their suffering is like our own – then ethical reasoning would lead nowhere. If emotion without reason is blind, then reason without emotion is impotent.

All the particular moral judgments we intuitively make are likely to derive from discarded religious systems, from warped views of sex and bodily functions, or from customs necessary for the survival of the group in social and economic circumstances that now lie in the distant past.

If penicillin had been judged by its toxicity to guinea pigs, it might never have been used by man.

It may be thought justifiable to require tests on animals of potentially life-saving drugs, but the same kinds of tests are used for products like cosmetics, food coloring, and floor polishes. Should thousands of animals suffer so that a new kind of lipstick or floor wax can be put on the market? Don't we already have an excess of most of these products? Who benefits from their introduction, except the companies that hope to profit from them?

In appropriate circumstances we are justified in using humans to achieve goals (or the goal of assisting animals).

Killing a defective infant is not morally equivalent to killing a person. Sometimes it is not wrong at all.

Surely there will be some nonhuman animals whose lives, by any standards, are more valuable than the lives of some humans.