This chapter explores Richard Kahn’s early life and studies at Cambridge. It focuses on the innovative elements of his fellowship Dissertation, The Economics of the Short Period, in relation to the genesis of the theory of imperfect competition. Other topics include the origins and contents of his 1931 article on the multiplier, and his presentation of the aggregate supply function in his early lectures. The chapter also covers Kahn’s collaboration with Keynes in the early 1930s, up to the publication of The General Theory, as well as Kahn’s early unpublished writings on international economic issues from this period.