  A theme of both the Second Discourse and the Letter to d’Alembert is the way in which human beings can deceive themselves about their own moral qualities. So, for example, theatre audiences derive enjoyment from the eliciting of their natural compassion by a tragic scene on the stage; then, convinced of their natural goodness, they are freed to act viciously outside the theater. Philosophy, too, can serve as a resource for self-deception. It can give people reasons to ignore the promptings of pitié or, as in Rousseau’s essay Principles of the Right of War, it can underpin legal codes (such as the law of war and peace) that the powerful may use to license oppressive violence whilst deadening their natural feelings of compassion.