One of the fun games some ontologists like to play is to define substance. Here is one of my attempts. And now here comes another:
- x is a substance in the strong sense if and only if x is not dependent on anything
- x is a substance in the weak sense if and only if x is not non-causally dependent on anything.
Notice that if the above definition is right, then an object that is dependent for its existence on its parts is not a substance even in the weak sense. One should be able to use this to argue for the Aristotelian axiom that no substance has parts that are substances.