Sunday, November 25, 2007

Parts and ownership

Some Aristotelians believe the following thesis: When a bit of matter comes to be a part of a substance, it ceases to exist. I.e., the bit of matter comes to be a part of a substance in the way in which a horse comes to be a corpse--the horse and the corpse are distinct entities, the corpse originating in the horse. If they believe this thesis, they have to give some explanation of why particles ingested can still be scientifically detected. They will do this either by saying that the particles no longer exist literally, but "virtually" do, or by saying that new particles just like the old ones come to exist out of the old ones, except the new ones have the essential property of being a part of substance that they have joined. There are two different reasons why one might believe such an outlandish thesis: (1) because one doesn't believe in parthood (Patrick Toner and Alexander Pruss incline in this direction), or (2) because one thinks that parts receive their identity from the whole (there is some textual basis in Aristotle for this).

I want to offer two arguments for this thesis, one metaphysical and Aristotelian, the second ethical and eccentric. I find the first plausible, and much less so the second, but the second is kind of neat, so I'll give it, too:

  • Matter receives its identity--that which makes it be the entity that it is--from the substance that it makes up. Therefore, if a bit of matter x is a part of substance A and a bit of matter y is a part of substance B, then if A is distinct from B, it follows that x is distinct from y. Therefore, no bit of matter can be a part of two substances. But everything that exists is a substance or a mode, relation, trope, accident or the like. A proper part of a substance is not a mode, relation, trope, accident or the like. Hence, if a substance has a proper part, that proper part is a substance. But the matter of a proper part A of a substance B would then be a part of both substance A and substance B, which contradicts the thesis that a bit of matter can't be a part of two substances.
  • This argument uses two main assumptions:
    1. Without receiving special normative power from you or some higher authority, the only way I can by myself make an item x that you presently literally own to cease to be literally owned by you is by destroying x.
    2. It is impossible for one person to literally own a part of another.
    Suppose now you literally own a carbon atom x (e.g., it's part of a steak that you own), and I without having received any special normative power eat the atom x so that it becomes a part of my body. By (2), I have made it happen that you no longer own x. But by (1), it follows (assuming I have received no grant of authority or the like), the only way I could have done this is by destroying x. Hence, when an atom becomes a part of my body, it is thereby destroyed.


Vlastimil Vohánka said...


Thanks for this, a very important issue.

Let me three very basic questions concerning your mereological nihilism.

1. In what sense - if, as you and P. Toner claim, no substance has a proper part - it is true that "my arm is my proper part"? For sure, there does seem to be something true about this common sense adage.

2. Do you claim that all substances (or all objects) are simple? If so, in what sense is God's simplicity special?

3. Is, e.g., a H2O molecule one simple substance or an aggregate of (three?) substances?

Alexander R Pruss said...


This is all very speculative. But:

1. I am inclined to deny that my arm exists. But it is true of me that I am two-armed--that is a mode of me.
2. Simplicity is, arguably, more than just lack of parts--it is also indecomposability. But we can be decomposed--parts can be made to come to exist, by removing bits from us. Moreover, we exhibit substance-accident complexity, while God doesn't.
3. If the H2O molecule "is" a part of me, then it doesn't exist, except "virtually" (i.e., it can be made to exist, and I have certain causal powers that make H2O molecule detectors go bing). If the H2O molecule is out in the real world, I am inclined to think it is an aggregate of at least three substances, but I do not know for sure. It could, on the other hand, be that H2O molecules can't really be distinguished out of background fields. I don't know enough physics there.

Anonymous said...


These arguments are both really great. I'll enjoy reading further comments on this.

P. Toner

Vlastimil Vohánka said...

Thanks, Alex.

You wrote: "it is true of me that I am two-armed--that is a mode of me."

Jiří Fuchs, a Czech Catholic Aristotelian, claims that (1) human body, e.g. my body, is a complex of a specific sort of accidents, and that (2) a human, e.g. I, is a simple substance which bears such accidents, it is modified by them (before I die and after my resurrection, in the meantime I have no accidents of that sort).

A substance is a being (ens) which is simple and in se. An accident is a being which is simple and in alio (it modifies a substance, the substance bears it).

On this conception also my arm seems to be a complex of a specific sort of accidents: a sub-complex of the body complex. No mereological nihilism - the complexes are pluralities.

Yes, I am a simple being, but I am a bearer of a complex of accidents.

My questions:

4. What is wrong with this view? (Which I like.)

5. Here is one possible problem. On the view, accidents - qua in alio - seem to be defined as beings which are properties (or something like that) of something different from themselves (whereas substances - qua in se - seem to be defined as beings which are not properties of anything). Thus my arm or a H20 molecule in my muscles is a property or a complex of properties. But that sounds strange. Maybe it is not strange to say that Aristotle's accidents - quantitas, qualitas, relatio, quando, ubi, situs, habitus, actio, passio - are properties (or something like that). But when applied to my arm or to the H2O molecule, it sounds like a fundamental categorizing error. One reason is that, e.g., my quantitas-accident *to be 176 cm high* or my situs-accident *to be sitting* are quite abstract entities (or abstracted by my reason); however, my arm or the H2O molecule are rather concrete and full-blood, they are rather things than aspects or properties of things. What do you think, Alex?

6. Maybe you would say the view of Fuchs is flawed because I am not the bearer of my body, because I am my body (?). In this case I cannot see how could I exist after my death.

Vlastimil Vohánka said...

... 7. You also wrote "parts can be made to come to exist, by removing bits from us". But if we have no parts, isn't it strange to speak as if there were some "bits" which can be "removed from" us? Still, such a talk is natural and expressing something real, at least it seems so.

8. "we exhibit substance-accident complexity"

Do you mean by this something different than Fuchs?

9. If, according to you, humans exhibit substance-accident complexity, then you do not hold that ALL objects are simple, with no proper parts. Am I right?

10. What are you reasons for allowing the substance-accident complexity of humans and for disallowing the claim that human arms exist? Where's the relevant difference?

Alexander R Pruss said...

It seems categorially wrong to say that my accidents are parts of me, or that parts are accidents.

However, there may be a grain of truth in the claim that parts are accidents. What I mean by that is that the statement that an arm is a part of me is made true by certain facts about my abilities (e.g., the ability to reflect light in certain ways, the ability to hit balls in certain ways, etc.) and about other modes of mine (e.g., my shape).

I agree that there seems to be more to the talk of "removing a bit".