Rauscher works mainly in the philosophy of Immanuel Kant. He has published work on Kant's ethics, political philosophy, metaphysics, philosophy of history, and methodology, but the central concern of his work is on Kant's metaethics and its relation to naturalism, realism, and cognitivism. He is completing a book on the topic. Additional research areas cover British Empiricists and German Idealists historically and the relation between evolution and ethics in contemporary philosophy. Rauscher has translated Kant's unpublished notes on ethics and is working on a translation of Kant's unpublished notes, drafts, and course lectures on political philosophy.