This chapter examines the manner in which the idea of progress is inscribed in arguments about international law. The chapter makes two central points. The first is that the impact of the idea of progress in international law should be measured not only in the context of paradigmatic narratives of progress but also against the pervasiveness of more prosaic uses. The second is that any argument that implicates progress, from the uppercase to the lowercase and back, is theoretical ‘all the way down’. While it may be hard to forsake the idea of progress altogether, the chapter argues that it may be even harder to defend as something other than a tired trope of legitimation.