In the development of a theory there becomes a time, when the ambiguities of academic research become distilled in the succinct form of a text book. In the development of Wolffian philosophy this distillation occurred with Thümmig's Institutiones philosophiae Wolfianae in usus academicos adornatae. The book appeared in two parts, firs of which dealt with the theoretical part of Wolff's philosophy – it covers issues dealt in Wolff's logical, metaphysical and physical works.
Summarising an intricate philosophical work is undoubtedly an achievement in itself, but one might wonder how original it can be. Then again, Thümmig's work was not completely without its novelties. While Wolff himself had written his main works thus far in German, Thümmig wrote in Latin, making Wolffian philosophy so available for an international audience. Indeed, many of the Latin terms used for concepts of Wolffian philosophy – e.g. ontologia – are fixed for the first time in Thümmig's work.
An interesting example of a terminological novelty is the notion of infinite judgements. In Wolff's logic judgements are divided into affirmative and negative judgements (respectively, ”A is B” and ”A isn't B”). Now, Thümmig mentions also a third possibility, where the form of the judgement is affirmative, but the predicate is negative (i.e. ”A is not-B”). The notion of infinite judgement was to be important later on, because it allowed Kant to classify judgements in triplets according to their quality (more of this when we reach Critique of pure reason.)
Now, it is undoubtedly questionable whether these terminological novelties were truly Thümmig's own inventions: the notion of ontology had appeared even before Wolffians used it and I suspect that same is true with the idea of an infinite judgement. Furthermore, it is doubtful whether Thümmig was really the first Wolffian to use these terms. A year later Wolff noted in a preface to a work on teleology that Thümmig's works were essentially faithful representations of Wolff's own doctrine. This makes one suspect that Wolff himself had already used the terminology in his lectures and private correspondences and Thümmig had merely wrote down what Wolff had said.
Whomever the real innovator is, Thümmig's book does contain in addition to terminological novelties also some substantial additions to and reworkings of Wolff's original writings. I shall discuss few of them in later blog texts, but for now I shall concentrate on the question of what was the ideal of science in Wolffian school.
Ever since Leibniz the field of truths had been divided into truths based on the laws of logic and truths based on empirical facts. Following this division, Thümmig speaks of a priori and a posteriori cognitions. The terminology is interesting. At least since Kant, philosophers have been accustomed to speak of a posterior cognition, based on experience, and a priori cognition, not based on experience. Now, this hasn't been the case always. Originally, a priori referred to reasoning that derived effects from their causes, while a posteriori reasoning referred to the opposite method of deriving causes from effects. I am sure that someone has already investigated the topic, but it would be interesting to know when exactly the two terms changed their meaning – certainly it happened then before Kant.
For Thümmig, a posteriori cognition was based in experience, while a priori cognition was based something called pure reasoning. Experience was the epitome of intuitive cognition that required a direct intuition of things. Judgements based immediately on intuitions concerned always individual things, and experience was a sort of generalization from intuitive judgements. The transition was possible, because at least the predicates of intuitive judgments were general and therefore even they had something to do with generalities. Thus, by knowing properties shared by many individuals we could discover empirical laws connecting certain general properties.
Pure reasoning, on the other hand, was the high point of symbolic cognition, which used words or other symbols to stand for things themselves. Reasoning in general had to do with making discursive judgements, that is, judgements deduced from other judgements by means of syllogisms. Reasoning was pure, when among the starting points of deduction there was no intuitive judgement, but everything was based on mere definitions and self-evident axioms.
As it was common at the time, Thümmig characterized mathematics as the primary example of a priori cognition – both Hume and Leibniz would have agreed that mathematics was based on self-evident axioms. We have seen that Rüdiger had criticized such an idea, because at least geometry appeared to have an intuitive aspect. Kant in a sense struck a compromise between the two positions, because on his opinion mathematics is both a priori and intuitive – here Kant had obviously changed the meaning of a priori and intuitive.
A primary example of a posteriori science is for Thümmig physics. Although Wolff and Wolffians were mistakenly thought to disparage empirical matters, we can immediately see that over half of Thümmig's book is dedicated to physical and hence empirical questions.
A more intriguing problem is where in the classification metaphysics should be situated. We have seen that Wolff at least apparently tried to axiomatize at least a major portion of metaphysics: everything begins from the self-evident principle of non-contradiction, while even the crucial principle of sufficient reason is supposedly deduced from it.
Thümmig, on the other hand, does not even mention this deduction. Instead, he emphasizes the justification that Wolff had barely mentioned – the principle of sufficient reason is required so that we can distinguish between a dream and reality. Thümmig thus apparently bases the main principle of metaphysics on an empirical proposition.
Does that make Thümmig's version of Wolffian metaphysics then a posteriori? Not necessarily. The possibility to distinguish dreams and reality is in a sense a necessary presupposition of even having experiences. We might hence interpret the justification as transcendental – metaphysics would then be synthetic a priori in the Kantian sense.
Next time I'll be looking at Thümmig's metaphysics in a more detail.