Marco Santi

Throughout the development of his views of relations, Kant takes Leibniz’s theory as a constant – though not fixed – term of comparison. In fact, Kant’s picture and evaluation of Leibniz develop as well. Kant is a stalwart advocate of the Physical Influx model of causality, which he equates with the reality of interaction relations. Leibniz’s view of the ideality of such relations, by contrast, entails Monadology and Pre-established Harmony. Kant’s premiss is the “Basic Insight” that we cannot conceptually grasp how two independent substances may relate to each other – a negative principle he maintains all along, from the 1755 “New Elucidation” to the Critical age. The Rationalist Kant still thinks that we can derive positive results about the intelligible world from this Insight – thanks to the “real use of the understanding” of the 1770 “Dissertation,” which he later repudiates. I show, however, that the “Dissertation” fails to disprove Pre-established Harmony and I argue that a “reformed” Leibnizian thinker may combine Monadology with Kant’s separation of the intelligible and sensible worlds. Crucially, this reformed theory reappears in Kant’s 1786 and 1790 texts. While the 1781 “Amphiboly” famously accuses Leibniz of the invalid real use of the understanding and of exchanging phenomena for noumena, Kant’s picture of Leibniz in 1786 is more favourable. The reformed Monadology, in which spatial phenomena do not mirror the Harmonic order of monads, is ascribed to Leibniz. Since this model is now seen as the only “correct intellectual picture of the noumena” (based on the Insight), and since it has only a negative function, Kant commends Leibniz as a forerunner of Criticism.