The debate regarding the interpretation of Kant's idealism is usually seen as turning on the best way to understand his transcendental distinction between appearances and things in themselves: that it marks either a contrast between two types of thing (the ‘two-object’ or ‘two-world’ view) or one between two sides or aspects of ordinary empirical objects (the ‘two-aspect’ view). But, even though I have long been associated with the latter camp, I have also thought for many years that this is not the most helpful way to frame the issue. The problem lies in an ambiguity inherent in the two-aspect view. It can be understood either metaphysically, as a thesis about the kinds of properties attributable to empirical objects, that is, as a form of property dualism in which these objects are assigned both phenomenal and noumenal properties, or methodologically, as a contrast between two ways in which such objects can be considered in a philosophical reflection on the conditions of their cognition. Accordingly, I take the fundamental question to be whether transcendental idealism is to be understood in the latter way or as a form of metaphysical dualism (whether as a thing or a property dualism being a matter of relative indifference). And I have further thought that the best way of addressing that question is through a consideration of the view which Kant opposes to transcendental idealism, namely, transcendental realism. If this realism is identified with a particular metaphysical doctrine then transcendental idealism must be as well; but if, as I maintain, transcendental realism cannot be so understood, then neither can Kant's idealism.
Kant’s Transcendental Idealism and Empirical Realism