The relation between transcendental idealism and philosophical naturalism awaits more careful determination, i. e. whether the issue of their compatibility hinges on their ontological view on the relation between physical and mental phenomena (i. e. whether it is supervenience or emergence) or on their epistemological view on our access to mental content. The aim of this paper is to identify a tension between transcendental idealism and philosophical naturalism, which lies not in their ontological view on the nature of substances, but (...) in their epistemological view on the relation between self-awareness and the first-personal access to mental content. I will first trace the (mis)understanding of transcendental idealism as Berkeleyan idealism to a misinterpretation of the self-knowledge premise in transcendental arguments. I will argue that transcendental idealism is not so much concerned with grounding reality of the external world as with establishing the agential nature of the first-personal perspective of experience, and it has an important implication on the meaning and function of self-awareness in transcendental idealism. (shrink)