Per se unity

The scholastics often follow Aristotle in saying that the matter and form in a living organism have 'per se unity'. What's that?

Well, the basic idea is that different ingredients can be tied together more or less loosely. Consider the following cases.

(i) Items in a pile of trash are tied together extremely loosely. It doesn't take a lot of force to separate them, and the items aren't held together in a pile because they each have some intrinsic power to join together.

(ii) Socrates and his pale color are tied together more tightly than a trash pile, but not so tightly that they can't be taken apart, so to speak. After all, Socrates can get a tan, in which case Socrates and his pale color are no longer together. It doesn't necessarily take a lot of force to separate them, for natural processes like getting a tan can do the job; we don't need God stepping in here. Also, Socrates and his pale color do have intrinsic powers to join together. Socrates has the (passive) power to be pale, for example.

(iii) Matter and form are supposed to be tied together far more tightly than either of the previous two scenarios. The way that matter and form come together to form 'one thing' is, for the Aristotelians, a paradigm case of unity. But like case (ii), it doesn't necessarily take a lot of force (like God) to separate matter and form, for natural processes like copulation and decomposition can do the job. And like case (ii), matter and form do have intrinsic powers to join together. Matter, for example, has the (passive) power to acquire a form.

The problem is, it's incredibly difficult to define 'per se unity', at least for the scholastics (it's also difficult for Aristotle, but I'm not interested in that here). There are a number of difficulties here.

I can define accidental unity like this: when a substance x (like Socrates) and an accident F (like his pale color) are tied together, x can survive the gain and loss of F. In other words, F does not determine the identity or persistence conditions of x. So x and F are tied together loosely enough that they can separated without x being destroyed.

One is then tempted to say that per se unity occurs when some x and F are tied together so tightly that they can't survive being taken apart. But that doesn't work. Here are some counter examples.

(a) Living organisms gain and lose matter all the time. Particles are constantly flying out of and into me, and biological cells are continually dying and being regenerated. I see no reason why an organism can't survive a total replacement of its matter. Aristotle, I think, says this somewhere (though I can't remember where, and I may be mis-remembering this fact). The scholastics also think so, but for an additional reason: they believe the body is restored (replaced?) after death, and most believe that God could miraculously replace a sick person's heart with a new, healthy heart, so mutatis mutandis for the whole body.

(b) Matter can survive the loss of a form, and indeed this is what happens in every normal case of change down here on earth. For example, when water is turned into steam, the scholastics (following Aristotle) would say that a chunk of matter first has the form of water, and then it loses that water-form and acquires a steam-form; but the matter is the very same throughout the whole process. As with all Aristotelian changes, the matter (by definition) persists throughout the change.

(c) For the scholastics, the soul can survive the loss of its body. They believe the soul survives for a time without its body, after it dies. Right now I have my body, but when I die, my soul gets separated from my body, and then it gets reacquainted (over coffee, probably) with a body in heaven.

So matter and form aren't inseparable. For all intensive purposes, it looks to me like they're tied together in exactly the same way that a substance and an accident is. Matter can survive the gain and loss of a form, and a form (like the human soul) can survive the gain and loss of matter.