German idealism
Franks' primary areas of research and specialization are Jewish philosophy, Immanuel Kant, German idealism, metaphysics, epistemology, the foundations of human sciences, and post-Kantian approaches within Analytic philosophy and Continental philosophy. His 2005 book, All or Nothing: Systematicity, Transcendental Arguments, and Skepticism in German Idealism, has been described as a "brilliant and highly stimulating book," "a truly indispensable book," which "attempts to answer a significant question ("Why were the German Idealists convinced that Philosophy had to have a single absolute principle, and that it had to be absolutely systematic?"), [and to] create a historical reconstruction of the emergence of German Idealism and show how German Idealism is still very much relevant to us today."