The only basis for inferring the nature of the cause of the universe would be if the universe (W) resembled human artifacts and productions (Ys).

We have experience of only one W (i.e., our experience of W is unique). Our experience of W is partial and incomplete (hence <W>), since we know only a small part of it in both spacial and temporal terms. We have no experience of any Zs at all. In these circumstances the only basis for drawing any conclusion about the nature of Z* from our (unique and partial) experience of W is by supposing that W bears some resemblance to objects such as Ys, broadly conceived to cover all human artifacts