I've already discussed the essentials of Wolff's theory of language when studying his German logic. What I especially emphasised at that point was the role of language in communication – since we cannot transmit our thoughts directly through telepathy, we have to use words that just suggest thoughts of certain concepts. In addition to this secondary role of being a surrogate of mental images, Wolff now also mentions a more substantial task of words as crucial for more abstract thought. Words are necessary for representing general terms that we cannot imagine, such as virtue, number or existence, and so, we might say, in these case words just are concepts.
The importance of words for abstract and general thoughts is especially clear in case of definitions, which often are the only way to produce certain abstract thoughts. Definition is for Wolff an essentially linguistic phenomenon, that is, it must be something either spoken or written. Definition should represent a certain concept, but not just any concept – it must be complete and determinate in the sense that through it we come to know enough characteristics for distinguishing and identifying the object of definition.
In effect, then, definition helps to make our concepts more clear and distinct. Before hearing the definition, we might have just an obscure idea of a concept referred to by a term to be defined. Definition then returns this originally obscure term to at least clear terms, that is, terms, the corresponding concept of which refers to objects we can distinguish from other objects. We might note how Wolff is here touching on the question known as the paradox of analysis: either an analysis of a term leads to an identical proposition or tautology and is thus useless or it leads to a non-identical proposition and is thus wrong. Wolff would admit that definitions are identical propositions, but would note that it is not the definition as such, but the whole process of defining and so clarifying our concepts that is important.
Definitions should then lead us to terms clearer than terms to be defined. This is actually one of the formal requirements of a good definition, according to Wolff. In addition, one should not use in definition the term to be defined or another term requiring the definable term for its own definition, because this would leave the original term as obscure as it was before.
Wolff also suggests that terms referring to modes of things cannot be used in definition: definition should be something that helps us discern things constantly, but modes are variable and therefore offer no reliable method for distinguishing things. For instance, suppose we have learned to identify a certain species of rabbits by the colour it has in summer. We still wouldn't be able to recognise it in the winter, if it happened to change its colour according to seasons. Instead, we would have to be able to recognise the rabbit through such properties it has constantly, that is, its essence and attributes. Note that these properties might be constant dispositions, provided that we can generate conditions in which these dispositions are activated. Thus, we can recognise different gemstones by the hues they present in certain lighting, because we can take the gem to be tested in the required lighting.
The ideal form of definition of a species of objects would, firstly, indicate the nearest genus to which the species belongs and then note how this particular species differs from other species belonging to that same genus. In essence, this is the classical mode of definition through genus and so-called specific difference, familiar especially from the traditional classification of animal species.
In speaking of definitions, Wolff of course mentions also the important difference between nominal and real definitions. What is important in this distinction is to note that Wolff did not uncritically assume that one could gain insightful theories just by putting words together: this would boil down to mere generation of nominal definitions, which do not imply anything about the actuality or even possibility of things so defined. Instead, one should aim to produce real definitions, which do allow us to say something about this and an important part of which is formed by genetic definitions telling how something can be generated.
So much for definitions, next time I shall be speaking of judgements.