A central message of Wolff's rational psychology was that the empirically observed nature of human soul is explained best, if it is assumed to be a force for representing the world, and most of this side of Wolff's system was spent showing how each distinct faculty could be reduced to such a force. With Baumgarten, on the other hand, this is more of an assumption already shown in the empirical psychology. Thus, Baumgarten uses most of the pages of his rational psychology for pursuits that overstep the limits of what we can experience, while with Wolff, these seemed more like an afterthought.
A commonality in Wolff's and Baumgarten's rational psychology is their belief that nothing material or no complex substance can account for soul's capacity to represent even itself. Baumgarten can then simply note that a soul as a simple substance is a Leibnizian monad. Although soul as such is then not a complex substance, it is attached to several such substances. Firstly, all the souls in the world form what Baumgarten calls a mystical body – this is evidently a reference to the idea of the church as the mystical body of Christ. Secondly, every soul is also tied up with some corporeal substance or body. This necessary relation to a body makes soul finite – its representations are limited by the position of its body.
An important matter for Baumgarten is the freedom of human soul. Baumgarten thinks that human soul must be free, because it can move its own body consciously. Of course, he notes, this is only possible, if pre-established harmony is accepted, because only then the (ideal) causation of the movement of human body is dependent only on the human soul. If either the influx theory or the occasionalism is accepted, the responsibility for bodily movement is taken away from the soul, because in both theories the decisions of the soul are determined externally, either by other bodies or by God.
After these relatively mundane concerns, Baumgarten heads straight into theological speculations. He at first notes that soul cannot have been generated by the parents – indeed, soul as a simple unit cannot have been formed out of a union of other substances. Then again, it might have been transferred to the body at the time of conception.
As for the end of a soul, as monads they cannot be taken apart and will continue their existence as long as world endures. This still does not mean that all souls would be immortal, since this requires some kind of personality, that is, conscious memory of having been alive before. Humans have such a personality and therefore probably continue their existence in the afterlife – Baumgarten also supposes that they will continue their moral progress, vicious people becoming more and more unhappy and virtuous people becoming more and more happy. Animal souls, on the other hand, are not personal in this sense – and Baumgarten speculates about a possibility of a whole hierarchy of souls, with different levels of awareness, in which human souls form only one stage.
So much for Baumgarten's psychology, next time I'll take a look at his theology.