Monday, April 13, 2015

Particle accretion and excretion in Aristotelian ontology

In Aristotelian ontology the matter and parts of a substance get their being from their substance. But now we have a problem: we constantly accrete (say, when eating) and excrete (say, when sloughing off skin-cells) particles. These particles seem to exist outside of us, then they exist as part of us, and then one day they come to exist outside of us again. How could their being come from our form, when they existed before they joined up with us—sometimes, presumably, even before we existed at all?

But suppose an ontology for physics on which fields are more fundamental than particles, and particles are like a bump or wave-packet in a field. Then we have a very nice solution to the problem of accretion and excretion.

Imagine two ropes. Rope A is tied by one end to a hook on the wall and the other end of rope A is tied to the end of rope B. And you're holding the other end of rope B. You rapidly move your end of the rope up and down. A wave starts traveling along rope B, then over the knot, and finally along rope A. We are quite untroubled by this description of this ordinary phenomenon.

In particular, it is correct to say that the same wave was traveling along rope A as along rope B. Yet surely the being of a wave in a medium comes from the medium and its movement. So we have a very nice model. Rope A has excreted the wave and rope B has accreted the wave. (You might object that in Aristotelian ontology, ropes aren't substances. Very well: replace them with strings of living kelp.) If the knot is negligible enough, then the shape of the wave will seamlessly travel from rope A into rope B.

I think one reason an Aristotelian is apt to be untroubled by the description is because we don't take waves in a rope ontologically very seriously, just as we shouldn't take kings in chess very seriously. They're certainly not fundamental. Perhaps they don't really exist, but we have merely adopted a mode of speech on which it's correct to talk as if they existed.

However, if a field ontology is correct, we shouldn't take particles any more seriously than waves in a rope. And then we can start with the following model. Among the substances in the world, there are fields, gigantic objects that fill much of spacetime, such as the electromagnetic field. And there are also localized substances, which are tiny things like an elephant or a human or a bacterium. The fields have holes in them, holes perfectly filled by the localized substances. The localized substances exist within the fields much like a diver exists in the ocean—the diver exists in a kind of hole in the ocean's water.

Next, pretty much the same kinds of causal powers that are had by the fields are had by the localized substances. Thus, while strictly speaking there is no electromagnetic field where your body is found, you—i.e., the substance that is you—act causally just as the electromagnetic field would. A picture of the field you might have is of a string whose central piece had rotted out and was seamlessly replaced with a piece of living kelp that happened to have the same material properties as the surrounding string. But you don't just do duty for the electromagnetic field. You do duty for all the fundamental fields.

Because you have pretty much the same kinds of causal powers as the fields that surround you, waves can seamlessly pass through you, much as they can through a well-installed patch in a rubber sheet. You accrete the waves and then excrete them. Some wave packets we call "particles".

Objection: When I digest something, it becomes a part of me. But when a radio wave passes through me, it doesn't become a part of me even for a brief period of time.

Response 1: We shouldn't worry about this. In both cases we're talking about non-fundamental entities. There are many ways of talking. For practical reasons, it's useful to distinguish those wave packets that stick around for a long time from those that pass in and out. So we say that the former are denizens of us and the latter are visitors.

Response 2: Perhaps that's right. Maybe we don't exist in holes in the fields, but rather the fields overlap us. However, when the fields are in us, we take over some, but not all, of their causal powers. The radio wave that travels through me does so by virtue of the electromagnetic field's causal powers, while the particles of the piece of cheese that I digest and which eventually slough off with my dead skin travel through me by virtue of my causal powers. The picture now is more complicated.


Mark Rogers said...

If you were of a mind to create an accretion field, just thinking about hurricanes, you might want to place it in the eye of the hurricane.

Heath White said...

What I don't get, from this description, is why e.g. cats are different from particles. In what sense does a cat occupy a hole in a field, other than the sense in which a particle would? And why are cats not mere field-disturbances, with the ontological status of particles-in-fields or waves-in-ropes?

Alexander R Pruss said...

I go back and forth on how to talk about it. One way to say it is that cats and people really do exist in a way in which waves don't. We know people really do exist, because we are them. And we know that cats really do exist because they are enough like people. Once one gets to the level of viruses, though, then I no longer know if we have anything but a field disturbance.

Alexander R Pruss said...

("Field disturbance" is a nice term. Thanks!)

Cameron said...

Hi Alexander, great article that got me thinking. Something to ponder though... We are electromagnetic being with billions of cells that are all electromagnetic organisms with which compose organs that are remotely controlled by the brain via electrical impulses. This means we are actually a field even if one is not present around us. Therefore, I would also reconsider the idea that "fields" passing through us can actually affect us and our fields creating either "disturbances" or "harmony". Thoughts?

Cameron said...

This was a response to reconsider this statement:

"Objection: When I digest something, it becomes a part of me. But when a radio wave passes through me, it doesn't become a part of me even for a brief period of time."

The radio waves may be just as true (and false) as the food analogy, where food existed outside of us, enters an exchange of energy with us (synergy?) where it is absorbed, processed and then excreted.

My question would be: How would a radio wave, sound wave, light wave or any other form of energy absorption/interaction/processing (ie- food) be any different?

This would help bolster your theory even more in my view by helping to "excrete" the above objection. :) hehe