After proving that soul or consciousness exists and that we can in some measure study it, Wolff begins to discuss the theoretical or cognitive part of soul. I might notice, by the way, that this is a rather common ordering, and indeed, I have never seen a philosophical study of consciousness begin with volition. The custom goes all the way back to Aristotle's De Anima, and presumably every philosopher has just copied his predecessors in this matter.
Before actually beginning to study any cognitive faculties, Wolff defines certain notions common to all of them, starting from the concept of faculty itself. Scholars of German philosophy are often so ingrained in the language of faculties that they fail to ask even what is meant by a faculty. Wolff actually defined the term already in his ontology, where it was explicated as any active potentiality, that is, any possibility to do something that was actually engaged with actualising this possibility. In other words, faculties of soul or mind are just capacities of mind to do something, but also not passive. Instead, they are active or actually use what they can do.
After faculty, Wolff continues by describing what is meant by clarity and distinctness of perceptions or representations. The notions themselves I have explicated quite sufficiently for a number of times: clarity means for Wolff ability to distinguish a perception, while distinctness means ability to recognise partial perceptions that help to distinguish the whole perception. I could still note one more time that these concepts should not be read as forming a strict division to e.g. clear and unclear perceptions. Instead, they work more as defining a scale of clarity and distinctness: we can distinguish an object with various accuracy in different situations, and analysis required for distinctness might reveal further characteristic marks. This notion is further backed up by the fact that Wolff calls clarity of perception light of soul – light does not form a clear division with darkness, but between light and total darkness there are many shadows and gray areas.
These very same perceptions can also be called ideas, although Wolff prefers defining idea as a representation, in which we are especially interested of the object represented: that is, when we talk of perceptions, we talk of an act of subject, but when we talk of ideas, we talk of individual objects. Concepts, on the other hand, are representations of general characteristics of things, of genera and species. Cognition, then, means acquiring ideas and concepts of various things, that is, conceiving what things and their characteristics are. Cognition can then have various levels of clarity, but Wolff places the most important distinction on whether the ideas and concepts involved are distinct, that is, analysed into further ideas and concepts. Cognition with distinct ideas and concepts is in Wolffian psychology on a level higher than cognition with obscure and confused ideas and concepts, that is, one should aim at analysing one's ideas and concepts.
Wolff begins the study of cognition from faculties of lower level. Wolff's choice reflects a natural development – we begin with confused and even obscure ideas, which little by little become clearer and more distinct. Thus, it is no wonder that Wolff begins with sensations, which presumably are the beginning of all cognition. Sensations are also the link of human cognition to the external physical world. An important element of this world is our own body that appears constantly attached to us and seems to be in continuous correspondence with certain perceptions (note how Wolff avoids the question whether this correspondence is explained by actual interaction between body and human mind or whether there is no interaction between them – such questions will be tackled in rational psychology). Sensation, then, is defined by the special correspondence between human mind and sensory organs of the body, that is, sensation is a perception that can be understood by basis of changes in these organs (even if they are not caused by these changes).
Because sensation is studied by Wolff in a part dedicated to the lower part of human cognition, it becomes natural to ask if Wolff completely discarded sensation as without any value and completely obscure. Yet, the idea of clarity and distinctness as a scale instead of division makes it possible that sensation could rise in clarity and even gain some distinctness. This is especially shown to be true by Wolff's investigation of attention and reflection, but even sensations themselves contain levels of clarity – a stronger sensation is also clearer than a weaker sensation. A further value of sensations lies in their relative freedom from arbitrary whims of human mind. Thus, if one is looking at some spot, one cannot just choose what one is seeing. The only way to control what one senses is to move to another spot or at least look to somewhere else.
So much for sensations, next time I shall turn to imagination.