Since ancient times, philosophers have maintained that to strive too hard for one's own happiness is self-defeating. - Peter Singer

We do not have to make self- sacrifice a necessary element of altruism. We can regard people as altruists because of the kind of interests they have rather than because they are sacrificing their interests.

The core of ethics runs deep in our species and is common to human beings everywhere. It survives the most appalling hardships and the most ruthless attempts to deprive human beings of their humanity. Nevertheless, some people resist the idea that his core has a biological basis which we have inherited from our pre-human ancestors.

Those who claim to care about the wellbeing of human beings and the preservation of our environment should become vegetarians for that reason alone. They would thereby increase the amount of grain available to feed people elsewhere, reduce pollution, save water and energy, and cease contributing to the clearing of forests; moreover, since a vegetarian diet is cheaper than one based on meat dishes, they would have more money available to devote to famine relief, population control, or whatever social or political cause they thought most urgent. … 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.