The paper is an analysis of the notion of the "auxiliary cause" (sunergon aition, henceforth AC) in Clement of Alexandria's Stromata. The starting point of the paper is the elaboration of AC in the so-called eighth book of Stromata (chapter 9), where AC is distinguished from preliminary (prokatarktika) and sustaining (sunektika) causes on the one hand, and joint causes (sunaitia) on the other, and where it is also described as a kind of prerequisits (hôn ouk aneu). A similar division of causes may be discerned in other parts of the Stromata (esp. books I, II, VI and VII), where the concept of AC is employed in the service of different apologetic and theological goals. We will explore these various contexts with the following questions in mind: 1. Does the "eighth book" present a coherent theory of AC? 2. Do other passages in which the concept is employed (Strom. I-VII) betray a coherent view of the same topic? 3. Are these explanations and applications of AC consistent with one another?