It is especially in Wolff's comments on empirical psychology where his wish to show the usefulness of his theories becomes evident. Wolff emphasizes that he has especially found two different types of faculties in human mind: cognitive and volitional. The study of cognitive capacities should generally help to improve our mental capacities and particularly help us to find a proper methodology for science. Wolff makes here some barbed strikes against Lange's Mental medicine, which he dismisses as a useless piece of charlatanry that wouldn't help anyone know anything.
Wolff's strategy for improving cognitive capacities is based on his attempt to quantify all mental capacities: capacity of memory can be quantifies by the number of new things a person can hold in his mind at the same time etc. On this quantitative basis Wolff can then make such useful recommendations as that capacities of concentration are improved in the morning, when there are still less distractive stimuli. Wolff's quantification goes in some cases further than with some previous philosophers. For instance, while Descartes thought that all people have an equal light of reason, Wolff states that this light varies according to natural capacities.
The aim of the education of cognitive capacities is to make one's ideas more distinct, that is, analysed. Although Wolff does define sensations in terms of distinctness, this does not mean that he would want to base science in some non-empiricist manner, which has become increasingly clear. Indeed, Wolff merely suggests that we should continue to analyse or conceptualize our individual sensations and so transform them into experience. Wolff thus wants to say that experience is something more than mere sensation: in a somewhat rasist comment Wolff even says that Hottentots, Lapponians and Samoyeds don't really have reliable experiences, although they undoubtedly sense things. The conceptual analysis of sensations turns them into experiences, which then can act as basis of scientific axioms.
Wolff appears to admit that the cognitive capacities of human mind are in some sense unfree. This is clear with sensations: we cannot choose that we'll see green, when we focus our gaze on a certain piece of grass. Furthermore, in case of conceptual reasoning there are also certain restrictions: if we are following a line of reasoning, the conclusion isn't haphazard, but follows from the premisses, perhaps true some psychological necessitation.
In contrast, Wolff emphasizes that human will is definitely free and capable of undetermined choice – an answer to the accusation of Wolff being a determinist. As we saw earlier, Wolff suggests that a person cannot will to do something he is not motivated to do, but that he can emphasize some motivation over the others. True, even the volitional part of human mind can become unfree, if mind is slave to its own affections. Still, this state of slavery does not prevent the possibility of a truly free action. Indeed, it is just such a task of becoming as free as possible that makes the study of volitional part of the mind important for morality and ethics.
Next time I'll turn to Wolff's comments on cosmology.