My aim is to advocate that we make this mental switch in respect of our attitudes and practices towards a very large group of beings: members of species other than our own - or, as we popularly though misleadingly call them, animals. In other words, I am urging that we extend to other species the basic principle of equality that most of us recognize should be extended to all members of our own species.

We wait until Pandora's box is opened before we say, "Wow, maybe we should understand what's in that box." This is the story of humans on every problem.

Philosophy ought to question the basic assumptions of the age. Thinking through, critically and carefully, what most of us take for granted is, I believe, the chief task of philosophy, and the task that makes philosophy a worthwhile activity.

I would not question the sincerity of vegetarians who take little interest in Animal Liberation because they give priority to other causes; but when nonvegetarians say that "human problems come first" I cannot help wondering what exactly it is that they are doing for human beings that compels them to continue to support the wasteful, ruthless exploitation of farm animals.

Should one break in and free the animals? That is illegal, but the obligation to obey the law is not absolute. It was justifiably broken by those who helped runaway slaves in the American South, to mention only one possible parallel.

Racists violate the principle of equality by giving greater weight to the interests of members of their own race when there is a clash between their interests and the interests of those of another race. Sexists violate the principle of equality by favoring the interests of their own sex. Similarly, speciesists allow the interests of their own species to override the greater interests of members of other species. The pattern is identical in each case.

If we compare a severely defective human infant with a nonhuman animal, a dog or a pig, for example, we will often find the nonhuman to have superior capacities, both actual and potential, for rationality, self-consciousness, communication and anything else that can plausibly be considered morally significant.