I discuss the philosophical significance of Kant's great cosmological work of 1755, the Universal Natural History. I discuss how Kant's interest in Newtonian universal forces led him to affirm a peculiar version of the physical influx theory. I argue that Kant's speculations about life on other planets are highly significant because they point to a key feature of Kant's theory of physical influx, namely that "the nimble motions of the body" stand as necessary conditions of the possibility of knowledge. This work directs us to an important topic that has received little scholarly interest: the relation between the body and knowledge in Kant's philosophical writings.
For nearly all of his career, Kant believed that the body stands as a condition of knowledge. One could trace the relation between the body and knowledge all the way from Kant's first published writing in 1747 to his monumental final work, the Opus postumum. One of the reasons why this element of Kant's philosophy has not been widely explored is that many readers have underestimated the significance of Kant's pre-critical works. Today I would like to discuss the philosophical significance of Kant's great cosmological work of 1755, the Universal Natural History.
Other commentators have focused on the scientific merits of this work almost to the exclusion of its extensive philosophical content. I believe that this work provides the key to understanding Kant's metaphysical system of physical influx. For those of you who are unfamiliar with this doctrine, it affirms causation between substances, for example between the soul and the body. (1) It competed with two other metaphysical doctrines, namely pre-established harmony and occasionalism. Up through the early part of the Eighteenth Century, physical influx was held in widespread disrepute. The standard objections to physical influx theories centered on problems with the alleged interaction between the soul and the body. First, the radically different natures of souls and bodies make them incapable of acting on one another. Second, any action by the soul on the body would violate laws of conservation of motion. Third, physical influx involves the metaphysically ridiculous claim that accidents migrate from substance to substance. More generally physical influx theories were also thought to lead to a determinism that was morally pernicious, namely because it undermines freedom, responsibility, and Scripture.
So much for historical background. Kant's theory of physical influx begins with his interest in Newtonian universal forces. This interest is in his Universal Natural History and Theory of the Heavens (1755), a work whose subtitle is Essay on the Constitution and Mechanical Origin of the Entire Universe, Treated in Accordance with Newtonian Principles. The plan of this work is to show how "general laws of motion" and "the accepted law of attraction" can be used to explain the development of the universe out of an original chaos...