What is Man?

Man has always been his own most vexing problem. How shall he think of himself? If man insists that he is a child of nature and that he ought not to pretend to be more than the animal, he tacitly admits that he is, at any rate, a curious kind of animal who has both the inclination and the capacity to make such pretensions. If on the other hand he insists upon his unique and distinctive place in nature and points to his rational faculties as proof of his special eminence, there is usually an anxious note in his avowals of uniqueness which betrays his unconscious sense of kinship with the brutes.

—Reinhold Niebuhr, The Nature and Destiny of Man, Chapter 1.