The final chapters in Darjesian empirical psychology concern the interaction of soul with the body. He is not yet trying to explain this interaction – explanations belong more to the next section or rational psychology. Thus, Darjes is now merely out to note the various situations where such interaction occurs.
Darjes begins by saying that we observe a certain complex entity or body as one constituent in my existence. Indeed, he notes, this body is a mechanistic machine or a system of non-spontaneous entities, and just like all machines, it can only work through motions. Now, at some situations we perceive that certain motions within my body – e.g. those occurring in my sense organs – correspond with certain cognitive states. When these movements stop, this specific cognitive state stops, when the movements change, so does the cognitive state, and finally, if some internal state of the body, like a disturbance in blood circulation, confuses the movements, the cognitive state becomes also confused and doesn't become clarified until the confused state of the body stops.
Clearly what Darjes has been describing is sensation, which is one type of the so-called inferior cognitive faculty. Yet, Darjes notes, not all inferior cognitive faculty need not have so close connection to motions of body. This is especially true of imagination, which associatively moves from one representation to another, which it has often been connected with. Thus, while the original representation might have a connection with actual motions in my body, the second representation might have no such connection. Furthermore, the association makes it also possible that superior cognition has some connection with motions of our body. In other words, we can use sensuous symbols to represent e.g. universal conceptions and so make it possible that motions of body awaken certain universal thoughts in us.
In addition to the relation of body with human cognition, Darjes also considers the relation of appetites and aversions with body. He firstly notes that appetites and aversions by themselves do not produce any motions in our bodies – if we just crave for food, this still does not make us do anything. One must also have made a decision on the means by which e.g. our hunger should be dealt with, and this decision of means will then be followed by movement of our body. Although body by itself is a system of non-spontaneous entities, because of this relation to spontaneous choices of human soul we can call certain motions of our bodies spontaneous and free. On the other hand, certain motions in our body have no such relation to spontaneous choices and can then be called forced motions.