When I investigated Wolff's German logic, I skipped a detailed take on most of the last half of the book, because it appeared to contain little of philosophical interest and seemed more like a haphazard collection of different topics. With Latin logic, I think I have a duty to be as thorough as possible and discuss also the final sections of the book, especially as the book is better organised, even if the topics dealt with would have no apparent philosophical interest.
Wolff's aim is to provide his students with a book on methodology. In addition to seeking truths, new scholars have to acquire new skills, one of which is the ability to write, read and review books. But before one can learn how to do all this, one must know what different types of books there are, because writing and reading, say, a historical treatise requires different things than writing and reading mathematics.
Every librarian knows that trying to place books into a neat taxonomy is ultimately a hopeless task: there's just too many possibilities to choose from. Wolff's approach begins actually from the standpoint of the method of book. Some books are merely historical or merely describe experiences concerning some specific topic. Thus, we have books on natural history, telling e.g. how cats reproduce, books on civil history, telling what has happened, for instance, in France and Germany in last couple of decades, and biographies that describe morally uplifting facets of someone's life (Wolff clearly lived before the age of rock stars).
In addition to historical, there are also dogmatical books, which are more about general theories than experiences: if you describe all the various changes of climate near the coast of Britain, you are doing history, but if you attempt to explain these changes, you are writing a dogmatical book. Note that there are clearly two ways to approach dogmatics. One can either just describe theory, without trying to justify it – this is essentially a historical take on dogmas – or one can use demonstrations based on axioms, definitions and reliable experiences and prove the dogmas – this would be a truly scientific treatise.
Wolff's classification is meant to give a clear answer to how such books are to be made and on what criteria they are to be judged. Here the methods for writing and judging books are parallel in the sense that the rules of good writing are essentially criteria for evaluating what is good. In historical books, one must consider especially the end of the book and on that basis decide what is to be told and in which order. An important question with historical books is the reliability of what is told – note that when you are reading a historical book, you can at most reach the level of Glauben or faith.
The methodology of scientific books is essentially the methodology Wolff has presented earlier. Thus, a scientific book should define its concepts as explicitly as possible, use only such premisses that are already known to be certain, that is, are either axioms or demonstrated propositions, or at least use only so-called lemmas that have been proven in other books – all standard Euclidean stuff. A point of interest is that Wolff notices the possibility of and condemns the habit of plagiarism, that is, an uncredited use of works of other authors.
While there are then strict criteria by which to decide the worth of a book, Wolff also suggests certain leniency in evaluation. Reader should especially try to interpret confusing words and propositions in the best possible manner which would make the most sense of the text – this is what is nowadays known as a principle of charity.
Wolff extends the use of the principle of charity also to hermenutics of sacred writings. The ultimate source of these texts is supposed to be God, whom we must assume to have perfect cognitive skills. Thus, what these texts say must indeed be true. Yet, because the writers of the texts have been imperfect human beings and God has just imported the thoughts contained in these texts directly to their mind, these texts are bound to have metaphors and even paradoxes, when the complexity of these thoughts has reached over the limits of the writers.
So much for books, next time we shall see what else was part of scholar's life in Wolff's time.