Over at Cogburn’s blog I noted that there’s a debate brewing over whether or not Kant advocates the thesis that we can know things-in-themselves. Of course, Kant’s thesis is that things-in-themselves exist, but that we can never have knowledge of them. Consequently, any knowledge we do have only applies to appearances or phenomena, or how things are given to us. Whether things exist in this way apart from us, the Kantian contends, is something we can never know. For example, things-in-themselves might be merely “thing-in-itself”, or a single unitary being without discrete entities. Sometimes it’s suggested that while Kant is a transcendental idealist, he is also an empirical realist. From the thesis that Kant is an empirical realist, it is then argued that Kant endorses the existence of the objects discovered by science as things-in-themselves. This severely misconstrues what Kant means by “empirical realism”. Let’s have a look:

I understand by the transcendental idealism of all appearances the doctrine that they are all together to be regarded as mere representations and not things in themselves, and accordingly that space and time are only sensible forms of our intuition, but not determinations given for themselves or conditions of objects as things in themselves. To this idealism is opposed transcendental realism, which regards space and time as something given in themselves (independent of our sensiblity). The transcendental realist therefore represents outer appearances (if their reality is conceded) as things in themselves, which would exist independently of us and our sensibility and thus would also be outside us according to pure concepts of the understanding. (CPR, A369)

Having carefully distinguished between transcendental idealism and transcendental realism, Kant then goes on to introduce the concept of empirical realism:

The transcendental idealist, on the contrary, can be an empirical realist, hence, as he is called, a dualist, i.e., he can concede the existence of matter without going beyond mere self-consciousness and assuming something more than the certainty of representations in me, hence the cogito ergo sum. For because he allows this matter and even its inner possibility to be valid only for appearance– which, separated from our sensibility, is nothing –matter for him is only a species of representations (intuition), which are call external, not as if they related to objects that are external in themselves but because they relate perceptions to space, where all things are external to one another, but that space itself is in us. (A370)

All “empirical realism” means for Kant is that objects (in the Kantian sense, i.e., as opposed to things) appear in space. However, here we must recall that for Kant, space is not something that belongs to things-in-themselves, but rather issues from mind as the form of intuition. Whether or not things-in-themselves are spatial is, for Kant, something we can never know. Clearly, then, Kant’s empirical realism is certainly know metaphysical realism about objects in space. Whether the world in-itself is anything like the world we know is, for Kant, something that we can never know. The claim that Kant was an empirical realist is not a rejoinder to the sorts of charges the speculative realists are leveling against correlationism.