When writing a Theory of Justice, John Rawls was clearly inspired by many theories of politics and ethics put forth by several famous philosophers. For example, Rawls cites the thinking of philosophers like Aristotle, Henry Sidwick, and Ludwig Wittgenstein. In particular, Rawls was inspired by the eighteenth-century German philosopher Immanuel Kant. Kant reflected on definitions and applications of justice in relation to the concept of a social contract, the idea of cooperation among citizens in a society. Rawls expands on Kant's discussions of a social contract by developing his own definition of justice. He explains that his theories of justice are an interpretation of Kant’s categorical imperative. He also develops Kantian theories about equality and ethics.

Rawls was also influenced by his contemporaries who also theorized about justice, such as William Van Orman Quine. Rawls met Quine while working at Harvard. The influence their meeting had on his work suggests that Rawls was likely also influenced by many of his fellow colleagues in academia.

And of course, Rawls was also influenced by the politics of the decades leading up to the book’s publication. The 1950s and 1960s were a tumultuous time for American politics and left political philosophers with a lot to reflect on in terms of what fairness, equality, and justice mean.