@DrYohanJohn Here he seems to be following Kant in a distrust that we can really know "the thing in itself" as we should. Or, enough; or maybe even at all, as you say. But when it comes to me accepting that you see a certain tree, for example, pretty much in the same way, and with the same results, that I see that same tree, and so we can therefore talk about it and compare notes, I'm a bit lost as to why this exchange cannot be at least a small step on building a knowledge base.