1.) A substance is what can be thought of without thinking about something else.
2.) Definition: the extended is the uniform, undifferentiated, infinite and spacial. It has parts outside of parts, is divisible, etc.
3.) We cannot think of roundness, elephants, particles, etc. without thinking about the extended, but we can think about the extended without any of these.
4.) Therefore, the extended is substance, all else in the physical world is not a substance.
5.) Therefore, in looking at the world by sense, we do not see its substance.
6a.) The relations between ideas are not the relations of extension (like left-right, up-down, inertial-accelerating)
7a.) Ideas are not of the physical world.
8a.) Ideas must exist in God. This is true of nothing in the world, even its substance.
9a.) Ideas are therefore necessary and eternal whereas the physical are not.
6b.) The substance of the world is invisible in itself. It is not what we look at when we open our eyes and see differentiation of color, texture, density, etc.
7b.) We would see the same beauties if they were produced within us without any realities outside of us. Thus beauty can be conceived of without the material world. Beauty is thus more substantial than the physical world.
8b.) Beauty is not of the substance of the world.
9b.) The intelligible world is more substantial than the physical world, as all of its reality can be present in ideas apart from the reality of the world.