Across its long history moral philosophy has been as concerned with the cultivation of certain moral dispositions, or traits of character, or moral psychologies, as it has been with establishing the validity and universality of moral rules and principles. Moral psychology begins with the inner person: not how we outwardly conform to external moral rules, but how we are in our hearts and souls and, particularly, how we are when we are truly flourishing as human beings. It is therefore concerned with the ethics of virtue, and a casual glance at the respective moral psychologies of Aristotle, Augustine, Spinoza, Hume, Kant, and the existentialists would reveal analyses of such virtues as integrity, justice, prudence, courage, magnanimity, sincerity, and authenticity. These are not innate dispositions, or inherited traits of personality like shyness or cheerfulness. They are acquired by teaching or practice or reflection, and to a certain extent reveal what we have made of ourselves; thus they express our moral way of being, and our fundamentl moral outlook, and not just something we happen to have.

Sartre's concern with the ethics of character, the conditions of self-determination and human agency, and the phenomenology of moral life, places him within this tradition of moral and philosophical psychology. This essay is concerned with elaborating and clarifying a number of interrelated aspects of Sartre's moral and philosophical psychology, particularly as they are developed in Being and Nothingness: self-determination and agency, responsibility for self, the unity of a life, moral reasoning, and self-knowledge.