[Ixa]

Is the existence of things-in-themselves self-contradictory, since things-in-themselves are non-ideas to which, therefore, no idea, e.g. existence, can apply? I think so, yet some materialists accept the thing-in-itself doctrine.
Engels said:

"The proof of the pudding is in the eating. From the moment we turn to our own use these objects, according to the qualities we perceive in them, we put to an infallible test the correctness or otherwise of our sense-perception. If these perceptions have been wrong, then our estimate of the use to which an object can be turned must also be wrong, and our attempt must fail. But, if we succeed in accomplishing our aim, if we find that the object does agree with our idea of it, and does answer the purpose we intended it for, then that is proof positive that our perceptions of it and of its qualities, so far, agree with reality outside ourselves."

When Kant says "experience" he means all possible experience, i.e. "the world". Hence "the identity of knowing and being". But that subject and object are two sides of the same reality is employed by both materialists and idealists.

The objective idealists and the materialists both, in some ways, seem correct to me. The arguments on both sides range from convincing to weak.

What is your view on materialism and idealism?