Human decision-making is complex. On our own, our tendency to yield to short-term temptations, and even to addictions, may be too strong for our rational, long-term planning.

The traditional view of the sanctity of human life will collapse under pressure from scientific, technological and demographic developments.

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.

Somebody who eats twice as much factory-farmed products as he or she needs to is clearly doing twice as much damage to the planet. From a utilitarian point of view, that's twice as bad.

Scholars have long dreamed of a universal library containing everything that has ever been written.

We may feel the pain of falling back from a level of affluence to which we have grown accustomed, but most people in developed countries are still, by historical standards, extraordinarily well off.

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.