I've been trying to explain Kant's transcendental idealism to a friend of mine. By transcendental idealism I am referring to a world of appearances which receive their character from the point of view from which they are seen (Kant's categories). I briefly went over Kant's subjective and objective deductions to demonstrate this. I talked about, as an example, that the world and the mind both obey non-contradiction (you could not imagine or experience/see a car that was both blue and not blue).
In response, he argued that there are plenty of things that we know exist in the world but cannot experience, bringing up the fifth dimension, for instance. Thus, he said, the objects/substances of the world are not a product of our minds.
How would Kant respond to this objection?
I asked a question like this a couple of days ago, but was too unclear about what I meant, misleading those who tried to answer me. So, I hope, this time I was clearer. Let me know if you have any questions.