The idea of good and evil has nothing to do with religion or a mystic conscience. It is a natural need of animal races. And when founders of religions, philosophers, and moralists tell us of divine or metaphysical entities, they are only recasting what each ant, each sparrow practices in its little society. Is this useful to society? Then it is good. Is this hurtful? Then it is bad.
Peter Kropotkin, Anarchist Morality (via philosophybits)