For those of you who still have some questions about what Aristotelian Natural Philosophy has to say about matter and form, here are some things that might help:
Step 1. Forget everything you think you know about matter (free your conceptual apparatus from the particular determinate ways you have learned to characterize the physical matter of bodies)
Step 2. Think about the dynamic relation between actuality and potentiality with respect to some thing; e.g., this water is hot (but it also the kind of thing that can be cold); this water is liquid (but it is also the kind of think that can be solid)
Step 3. Think about the forms of the thing as what the thing is in actuality at some given point in time (e.g., hot water)
Step 4. Think about the matter of the thing as the potentiality of that same thing to exhibit some form at some time and/or to exhibit some other form at some other time (i.e., to be hot or cold, to be liquid or solid–while still being water)
Okay, so a substance (or what exists in the most fundamental sense) is some determinate thing that remains the same thing or retains its identity—regardless of whatever changes may occur with respect to its particular properties and its particular states.
What is constant through these changes?
- It is not all of the actualities, or the particular properties it has, or states it is in, at some given point in time (i.e., form).
- It is the potentialities that it has just as much when it actually has these properties, or is actually in these states, as it does when it does not currently have these properties or exist in these states (matter).
Water is matter-formed in a particular way that explains why it has the potentialites it has (i.e., to be actually hot at the same time that it is potentially cold, and to be actually cold at the same that it is potentially hot)
So, for Aristotle, matter is not a substance. Matter alone is not something that exists in its own right and can be conceived in itself.
For matter, to exist is to be the potentiality for some really existing thing to exhibit some substantial form and to take on some range of other forms that are characteristic of things of that kind—Matter does not exist in its own right without form, and we cannot conceive of matter except as being actually informed in some way.
For form, to exist is to be the actuality of some really existing thing–Form does not exist in its own right without matter, and we cannot conceive of form except as being instantiated in some matter.
Form and matter are two aspects of the same really existing thing (considered, now, as it actually is at some point in time, now, as it has the potential to be whatever it actually is, but also to change properties or states in ways that are consistent with it remaining the same thing).
These kinds of consideration are crucial to Leibniz’s divergence from Descartes concerning res extensa and from Spinoza concerning extension as an attribute of substance. The geometrical conception of bodies–in terms of continuous quantities of extension in three dimensions–is an incomplete and abstract conception, according to Leibniz’s view. It is not a representation through which we think some thing that exists in its own right. It is, rather, a representation through which we think/imagine the set of possible shapes, sizes, and positions that things can have (potentiality without actuality).
In order for us to represent anything real or substantial in bodies, we need to think the active powers (formal principles) that explain both the capacities for bodies to be extended (in particular ways that we define quantitatively in terms of shape and size) and to act on and be acted upon by other bodies (to move and to be moved).
Without this, there is no distinction between geometry and physics. The latter cannot provide explanations of phenomena by appeal to the natural principles that give rise to these phenomena (i.e., the fundamentally real things composing the natural world) if it begins with a conception of bodies merely as extended and changeable and treats natural change simply as changes in the size, shape, and spatial location of modes of extension.
More on that to come…