Some Steps towards a Transcendental Deduction of Quantum Mechanics

My purpose in this paper is to show that the two major options on which the current debate on the interpretation of quantum mechanics relies, namely realism and empiricism (or instrumentalism), are far from being exhaustive. There is at least one more position available; a position which has been widely known in the history of philosophy during the past two centuries but which, in spite of some momentous exceptions1, has only attracted little interest until recently in relation to the foundational problems of quantum mechanics. According to this third position, one may provide a theory with much stronger justifications than mere a posteriori empirical adequacy, without invoking the slightest degree of isomorphism between this theory and the elusive things out there. Such an intermediate attitude, which is metaphysically as agnostic as empiricism, but which shares with realism a committment to considering the structure of theories as highly significant, has been named transcendentalism after Kant. Of course, I have no intention in this paper to rehearse the procedures and concepts developed by Kant himself; for these particular procedures and concepts were mostly adapted to the state of physics in his time, namely to Newtonian mechanics. I rather wish to formulate a generalized version of his method and show how this can yield a reasoning that one is entitled to call a transcendental deduction of quantum mechanics. This will be done in three steps. To begin with, I shall define carefully the word “transcendental”, and the procedure of “transcendental deduction”, in terms which will make clear how they can have a much broader field of application than Kant ever dared to imagine. Then, I shall show briefly that