The density of human population combined with the development of powerful and largely unconstrained technology has given us the problems of the anthropocene and the serious possibility of self-caused extinction.

The idea that we would raise billions of sentient animals, treat them horribly, pollute our waterways with their waste, compromise the effectiveness of our antibiotics so that they grow faster, and then slaughter them with little regard to their suffering so that we can feed off their corpses, will seem to most people unthinkably cruel and barbarous - sort of in the way that we think of medieval punishments, or Europeans today think of the death penalty.

A great deal of our math, science, philosophy, and everyday behavior presupposes that stability and equilibria are the "default" states, and everything else involves some "perturbation." This is a mental model, a conceptual frame, a tacit belief, a presupposition - whatever you want to call it.

Environmental problems provoke challenges about what kind of world we want, how important we think it is if something is brought about by human action or by brute nature, what we think of the value of human life compared to that of other living things.

Most of what we think of as distinctively human has occurred in the last 10,000 years in the Holocene - a period in which the Earth was abnormally quiet.

Attitudes are changing very quickly.

Bentham spent much of his life writing constitutions and proposing legal reform in the light of his utilitarianism. The evaluation of particular acts was hardly his concern. The psychology of his day was hedonistic and he worked in that framework and passed it on to Mill, but it is clear as day that Mill was not a hedonist in the sense in which we use that term today, though he used the language of pleasure and pain to express his views.