"Transcendental idealism is a form of empirical realism because it entails that we have immediate (non-inferential) and certain knowledge of the existence of objects in space merely through self-consciousness:

[…] external objects (bodies) are merely appearances, hence also nothing other than a species of my representations, whose objects are something only through these representations, but are nothing separated from them. Thus external things exist as well as my self, and indeed both exist on the immediate testimony of my self-consciousness, only with this difference: the representation of my Self, as the thinking subject is related merely to inner sense, but the representations that designate extended beings are also related to outer sense. I am no more necessitated to draw inferences in respect of the reality of external objects than I am in regard to the reality of my inner sense (my thoughts), for in both cases they are nothing but representations, the immediate perception (consciousness) of which is at the same time a sufficient proof of their reality''. 

Kant/SEoP