Complex sentence: He thinks only of his own personal happiness and the unfairness of the situation in which he has been placed but gradually comes to recognize his membership in a larger human community, which makes demands on him that he cannot ignore.
Split into simpler sentences: He thinks only of his own personal happiness and the unfairness of the situation in which he has been placed. But gradually he comes to recognize his membership of the larger human community, which makes demands on him that he cannot ignore.