Materialism is the view that all that occurs, occurs in dependence on material causes. Without such a view, it would be very difficult to engage in physics, since the outcome of any experiment could be interpreted as being the result of non-physical causes. The notion that physics is a complete system, covering all of reality, is a very daring one indeed. It is really only during this century, that such a notion can be defended seriously. According to relativity theory, it includes energy as well, and according to quantum theory, we can no longer talk about uniquely defined states of being.
Actions act, without anything extra required.
That seems to me to be the most straightforward interpretation of what quantum mechanics tries to tell us. It is a fascinating outcome of twentieth-century physics that materialism has tended to converge to phenomenology. Phenomena are understood in ever greater detail, while previous explanations of properties in terms of things that have those properties are being abolished. Properties is all we deal with. Phenomena have become more concrete, matter has become more fluid, and the two have lost their sharp separation.