A Study On The Problem Of Third Thing Of Synthetic Judgement A Priori In Kant

The synthetic judgements a priori that can be possilbe need a third thing, which combines the subject and predicate of the judgements. Critique of pure reason and Groundwork for the Metaphysics of Morals interpret deeply and systematically the sense of the third thing.In Critique of pure reason, Kant mainly refered the third thing of pure mathematics、pure natural science, but refered to the third thing of transcendental natural metaphysics a little."The introduction"of Critique of pure reason has clearly showned that the intuition is the third thing which combines the subject and predicate of mathematical judgements. Some discussions in "transcendental aesthetic" and "transcedndental doctrine of method" indicated that the intuition is a priori(space and time), but not empirical. Schlick denied that there is no intuition a priori, which is the due sense of denying the existence of synthetic judgements a priori. In fact, Schlick refuted Kant’s theory of intuition a priori by the developments of contemporary mathematics, which can not be successful because it is an external refutation.Kant’s "pure natural science" is the natural metaphysics as such and the corporeal natural metaphysics(rational physics)."The introduction" of Critique of pure reason by an example has prelimilarily prompted that the third thing is mere concepts which combine the subject and predicate of the judgements of pure natural science. Some discussions in "transcendental analytic"and"transcendtal doctrine of method" which further indicated that the third thing is categories. Although there are three third things which have different meanings in pure natural science, which are transcendental schema, a whole condition which is composed of inner sense、imagination and apperception and categories. Our studying suggests that categories is the third thing which combine the subject and predicate of judgements in pure natural science.The transcendent natural metaphysics is composed of three parts, which is psychology、rational cosmology and rational theology. The three parts respectively study the soul、the world and the god. In transcendent natrual metaphysics, it may not be produced the judgements which are similar to constitutive synthetic judgements a priori in the pure mathematic and the pure natural science, there are only regulative synthetic judgements a priori which are three priciples of reason, i.e. unity、diversity and continuity. But, Kant hasn’t given out the logical expression and little refers to the third thing of them, which has become a major problem in the research of Kant’s philophy.In Groudwork for Metaphysics of morals, Kant clearly identified that the categorical imperative is a synthetic practical proposition(judgement) a priori. How is a categorical imperative(which is a synthetic judgement or proposition a priori) possible? It is concerned with the problem of third thing of categorical imperative. Around "what is third thing of categorical imperative?", there are two trains of thoughts in demostic and foreign scholars, i.e.mixed and a priori. Analytics indicates that the autonomouswill is the third thing of categorical imperative.The concept of synthetic judgements a priori what Kant raised suffered serious suspection from analytic philosophy. The major object of suspection is distinction between analytic and synthetic judgement; the focus of suspection is the concept of analysis. Although analytic philosophy’s suspections has important significances, there are some problems. These problems include the lack of meaning to clarifying the concept of analysis, discriminating the significances of distinction between analytic and synthetic judgement, and lacking the due attention to synthetic judgement a priori. Analytic philosophy’s suspection is related to the criterion of knowledge. The synthetic judgement a priori as a criterion of knowledge has its reasonable factors, which is that not only has university and necessity, but also extend to human’s cogintions. So, the criterion of knowledge shouldn’t has only one, but many.The third thing of synthetic judgemts a priori has double aspects in the pure mathematics、the natural metaphysics (including the pure natural science and the transcendeant natural metaphyiscs). The third thing of categorical imperative has also the double aspects. The third thing as medium has groudwork for the synthetic judgement a priori in logic、 epistemology and metaphysics. In different discipline, the third thing is different. The problem of third thing is universal, it is a clue for Kant’s philosophy and has important significances to study Kant’s philosophy, even to the contemporary western philosophy.