When we see matter as the parts that remain though change, the arguments for materialism become clearer and more convincing. This is a good thing – a metaphysician must start off as a materialist since he attempts to explain all things, and the simplest such explanation is that they are all material or sensible or tangible, etc. The arguments below are a bit longer than they need be – most can be seen in an intuitive glance, namely the first glance at all things which, for a human being, should be materialistic.
Matter is what remains though change. The simplest way to understand this is that various parts are gathered together and separated – that is, that all change is change of place or position. But to change place does not change the nature of the thing that changes place (no one says that moving something from here to there gives rise to a different thing.) Given the definition of matter, it follows that it doesn’t change its nature by the change. Now in order for materialism to be false, there would have to be some nature different from matter, but no such nature ever comes to be.
Again, if there were a new and unique nature, it would have to arise from matter. But each material part has its own nature before the change, therefore it must get a new nature after the change. Therefore we must posit some other matter that allows matter to change from one nature to another, and then another matter for that matter, ad infinitum.
Again, the definitions we give of things have to be able to do real work in illuminating the natures we are dealing with. Aristotle insists on this as much as anyone, saying in the De anima that a definition that doesn’t show us the properties of a thing is simply worthless. But to see natures as simply collections or conglomerations gives us the greatest illumination about what they are, since it allows us to understand them as machines, and therefore in relation to what we know best.