A
mousetrap can catch a mouse, but it can also catch a small rat, or a large bug, or a rolling ball of paper. It cannot catch a puff of smoke, or a Ford F-150. The mousetrap is organized in such a way that it can capture a certain subset of the world, linked together by mobility, size, materiality, etc. If we ask why a mousetrap was sprung, the answer will always be in the form of some object that has a particular kind of relationship to the mousetrap. "Because of the movement of particles" is not a real answer.
What moves the human mind to action? Let's say my friend calls me on the phone to tell me that The Big Lebowski is just starting on channel 52, so I turn on my TV to watch (no one watches TV anymore, but humor me). Or, my friend texts me with the same information -- I turn on the TV to watch. Or, my friend leans in the window to tell me in person that the movie is startin -- again, I turn on the TV to watch. What is the cause of my turning on my TV? Saying "the movement of particles" ignores that only certain "particle states" move me to watch the TV, while others do not. When we ask "why", we want to know what is in common between these situations.
The answer is that I very much like the Big Lebowski, and have the information that allows me to find and watch it. That is, I have been supplied with a reason. That reason is what is in common between the three different scenarios that all end with me watching channel 52. The human mind is a mousetrap of reasons. Yes, there were material things that needed to happen for me to receive the information I wanted. But what materialists fail to grasp is that intentional beings use the properties of matter to further their own ends. We are made of matter specifically because we can use our own matter and the matter of the world to pull reasons out of the universe, reasons which give us cause to act. Matter is the medium, not the final cause.