According to Kant, all events in nature are subject to the principle of causality. Nevertheless, free actions are possible, because freedom and the universal law of causality are compatible without contradiction. Quantum mechanics is indeterministic, i.e. it implies a violation of causality. It is shown that: 1) this indeterminism can be understood by means of a continuation of Kant’s transcendental philosophy, as it is, like determinism, just a special type of universal causality, occurring when objects are not completely determined, 2) (...) quantum mechanical indeterminacy must not be identified with freedom, because it occurs only within the realm of sensible appearances existing in space and time, whereas freedom belongs to an intelligible substratum that is not part of the sensuous world. (shrink)

Summary The question underlying this article is whether the Kantian transcendental philosophy is wide enough to constitute the objects of quantum physics as objects of possible experience and consequently to found the objectivity of quantum physical knowledge. It is shown that the Kantian determinations of the categories (quality, substance, causality) can be interpreted and elaborated in such a way that the quantum physical concept of an object characterized by nonobjectivity of properties is conceived. Therefore the categories are valid in quantum (...) mechanics and warrant the objectivity of quantum physical experience. By the interpretation of the Kantian infinite judgement as an indefinite proposition it is possible to define the non-objectivity of properties categorially as indefiniteness of qualities. In particular by the indefiniteness of the position-quality the non-permanent localizability of quantum mechanical objects can be understood a priori. However the object of possible experience, especially the quantum mechanical object is underdetermined by the categories of substance and causality: If the object is determined to be a substance it is not yet conceived to be an individual; its characterization by means of probability laws is categorially indeterminate. In so far the significance of transcendental philosophy for the foundation of quantum physics is limited. (shrink)