physicalism is that it attempts to reduce everything to one layer of understanding. Physicalism does not on its own include encapsulation. We are not encouraged to manipulate the sum of the parts as something new and different than the crude bag of parts. Which is why emergence often does not make sense in the physicalist framework. To understand something we must understand the physical layer. This is an incorrect approach in my experience of system design. Essentially, I'm saying that on closer scrutiny ex nihilo nihil fit ("nothing comes from nothing") is in some sense incorrect.
My argument against a pure physicalist view is diagonality. I can create two functions: one to move an element left-right and another to move the element up-down. When applying both functions to the element, it will move diagonally. Diagonality does not exist in either of the two functions. It exists only in the element as an interaction between the two functions, that is to say in the "negative" space (in the "nothing") bewteen the two. It emerges from something we cannot experience except in the relationship between the parts, perceived as a single whole as they interact.
There is a concept of supervenience in physicalism that I can perhaps agree with. Take my diagonality. If you alter the left-right movement, you will alter the diagonailty. With other words, diagonality supervenes on the two functions. But physicalism seems to constantly implore us to go deeper, until we are dealing with vectors in a Hilbert space. However, reduced to that level, we can no longer see the forest for all the trees. Instead of extending our knowledge we have eliminated a part of it by by blinding us to the supervening and focusing entirely on the supervened.
For a deep understanding, it's not sufficient to break everything down into pieces. We must shift our attention between multiple experiential tiers. Common sense notions are as valuable as hard to access notions about angular momentum. In the immediate sense, folk psychology and such are more valuable. What is of greatest immediate use to us is what will carry us through the day. I don't need to understand combustion to understand the power of fire. Yet to fulfill the Basic Imperative, we must extend ourselves as deep into the bizarre as we can. However, if we get stuck there, we will be lost and unable to fulfill it. The trick to mastering our world is to continuously shift between levels of decomposition and not superficialize one or the other.