Along with Fischler, Shenker, and Susskind, he is one of the four originators of M(atrix) theory, or BFSS Matrix Theory, an attempt to formulate M theory in a nonperturbative manner. Banks proposed a conjecture known as Asymptotic Darkness - it posits that the physics above the Planck scale is dominated by black hole production. He has often criticized the widely held assumption in the string theory community that background spacetimes with different asymptotics can represent different vacua states of the same theory of quantum gravity. Rather, Banks argues that different asymptotics correspond to different models of quantum gravity. Many of his arguments for this and other ideas are contained in his paper "A Critique of Pure String Theory: Heterodox Opinions of Diverse Dimensions." published in 2003.