Love plays an important role in Rawls’s early thinking about justice. First, the idea of love is crucial in A Theory of Justice to his account of how citizens come to acquire a sense of justice and the accompanying moral psychology that is essential for its development. Second, Rawls uses the concept of love as an analogy with the concept of justice to explain why citizens would accept the possible liabilities and losses of acting justly. Third, he discusses the idea of the love of mankind in his criticism of classical utilitarianism. Finally, Christian love is the topic of Rawls’s posthumously published undergraduate senior thesis.

In the third part of A Theory of Justice Rawls moves on from the task of justifying the principles of justice to the difficult question of the motivation citizens have to take these principles as their own and to abide by their requirements. While Rawls later abandons the theory of congruence between the good of citizens and the requirements of justice that he develops in this part of A Theory of Justice, he retains the moral psychology that he elaborates in these pages. Rawls assumes at the outset of his theory that citizens have a sense of justice, understood as a moral feeling or sentiment that motivates them to abide by their rationally chosen principles of justice. A sense of justice is developed in three stages and love plays its crucial role in the first stage. These are stages of childhood during which moral feelings, necessary for democratic citizenship, are developed. In his somewhat speculative discussion of the first stage Rawls assumes the truth of a psychological law that a child, initially motivated by rational self-love, will come to genuinely love her parents when they “manifestly love” their child, and in loving their child they affirm the child’s sense of worth. In these circumstances the capacity to love others develops as a consequence of being the recipient of unconditional parental love. The reciprocity between self-love and the love of others suggests another conceptual reciprocity between the rational and reasonable that Rawls explicitly developed in later work.