Three related problems form the background to Deleuze's development of the concept of reciprocal determination in Difference and Repetition. The historical importance of these problems and the power of the concept in resolving them explain its pivotal role in Deleuze's work. Indeed, it is questionable whether Deleuze's metaphysics can stand without reciprocal determination. Given the strong connection between Deleuze's and Whitehead's philosophies and their common background in the problems to be outlined below, this chapter asks whether a parallel idea of determination can be found in Whitehead's work.² It will be shown that such parallels exist through many of Whitehead's books and essays, but that there are significant and productive differences between the two positions.