In an interview, Deleuze remarks that The Fold was a very important book for him because it allowed him to distinguish the Concept from the Affect and Percept, which he suggests he had previously confused in the Refrain Plateau, of A Thousand Plateaus (N 137). This remark is very significant because elsewhere Deleuze explicitly links affect, percept and concept with Spinoza's three types of knowledge (N 164–6); and yet this is all the more problematic in that one looks in vain for these terms within The Fold itself. So it appears that a relationship between Leibniz and Spinoza is both posited, and yet apparently occluded, and all the more so, as Deleuze in The Fold, unlike earlier works, is keen to stress the differences between the two thinkers (TF 44, 106). This last point reminds one that Deleuze, by the time of The Fold had developed many previous positions on both Leibniz and Spinoza, all of which are subtly reworked within The Fold itself. The aim of this essay is to go back to these earlier encounters with Leibniz and Spinoza, and by examining exactly how Deleuze habitually links these two philosophers, to elucidate exactly what The Fold might be clarifying, and what might follow on from this clarity.