I am currently reading "Real Essentialism" written by David Oderberg. He discusses the issue of substance individuation. The principle of individuation is matter. Now if we have Plato and Socrates, then they share the same form (of course understood in abstraction) but they differ in matter. Now he presents the problem discussed by Fine where Plato is eating Socrates at breakfast and slowly the matter of Socrates replaces the matter of Plato. After this process Plato consists of the same matter as Socrates, therefore Plato and Socrates are identical.

Oderberg solves this problem by adding a time index to matter. Then Plato consists of the same form and matter as Socrates, but at different times, so they are not identical after all.

But why assume that they consist of the same matter in the first place? Socrates is unified substance. He is matter formed by his substantial form. Now when Plato is eating Socrates, then (assuming he is alive) he gradually loses his matter. But then detached matter is substantially changed (it is no longer formed by Socrates' form and it has, for a short period of time, its own separate existence). So first some "chunk of matter" is part of Socrates (formed by his substantial form), then it is formed by some other form, and next it is formed by Plato's form.

But substantial changes seem to exclude the possibility of talking about the same matter, because we have different subjects of predication.

  • I made some edits for grammar and spelling. You are welcome to roll them back if you feel they are inappropriate. Welcome to this SE! May 23 '18 at 2:04
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    The issue is debated since A's time : see Aristotle : The principle of individuation. Ref. Met,vii 8, 1034a5–8: "And when we have the whole, a form of such a kind in this flesh and in these bones, this is Callias or Socrates; and they are different in virtue of their matter (for that is different), but the same in form, for their form is indivisible." May 23 '18 at 7:00
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    The issue is that A's theory accounts for individuals in terms of different instances of the same essence (see Type-Token): being spatio-temporally different, two instances are clearly not identical, like two bricks produced from the same mold. But this does not fit with our "feeling" about human individuality, based on mind/ soul/ consciousness. May 23 '18 at 8:11
  • I still have one doubt concerning one position from Encyclopedia and it may stem from differences between Oderberg and Aristotle. Oderberg claims, following Thomists, that every substance has only one form. So let's take water as example. It is composed of oxygen and hydrogen. He says that there is no actual oxygen and hydrogen in the water. Those particles exist only virtually in the water and can be recovered from the water. They exist ont as compounds in their own right but as elements fully harnessed to the operations of the water. May 23 '18 at 10:36
  • So if I recover those particles from the water, should I say that they were identical with those in the water or not? I guess not, because these object are now formed by form of atoms and inside water they had no form whatsoever, because they were formed by form of water. May 23 '18 at 10:41

See J. Lukasiewicz, E. Anscombe and K. Popper, Symposium: The Principle of Individuation (1953), page 93-on (Anscombe) :

The statement that matter is the principle of individuation does not mean that the identity of an individual consists in the identity of its matter. Thus it is not an objection against it that the matter of a man's body changes in the course of his life.

if by " What is the principle of individuation?" you mean, or include, the question " What makes a man the same man at different times ? "- then the answer " matter " is an absurd one. But as we are talking about Aristotle we have no right to take the question in that second sense at all.

this demonstrates quite clearly that if you mean anything Aristotelian by calling matter the principle of individuation, you do not mean that the identity of a person is the identity of the matter of which he is composed.

The debate has been followed by :

and :

Of course, in modern terms, thing are more complicated: we can agree that humans are made of a "stuff" of atoms, that qua atoms are identical from a qualitative point of view.

But atoms are organized in different human beings in different ways by DNA.

  • Thanks for your answer. Could you please verify if my following statement has sense or it rather stems from some profound misunderstanding. I assume that my body is simply prime matter informed by my soul. My soul is wholly present in every part of my body. May 23 '18 at 15:03
  • This souls informs my whole body and its every part. Therefore if atom is part of my body, it is again prime matter formed by soul. Now this atom has many properties of actual atoms, though not all of them. If this "atom" is released from the body, then it undergoes substantial change and now it is real atom not identical with that one which was present in the body. May 23 '18 at 15:03
  • I am just trying to make sense of position according to there may be only one form in the body.. Your point about structure of atoms looks well if we have some hierarchy of forms in the living organism. May 23 '18 at 15:36
  • @SekstusEmpiryk - according to A, there is only one form for the human being: its essence or soul. May 23 '18 at 17:34

According to A. Bailey, there is a goal ahead of every atom and the goal of an atom in the human body is to become a human. I would venture that if some atoms of a body are removed from that body then they may form part of another body if absorbed or integrated into it.

"For all the different grades and types of atoms there is a goal and a purpose also. There is a goal for the atom of chemistry; there is a point of achievement for the human atom, man." The consciousness of the Atom. Page 68. https://www.lucistrust.org/online_books/obooks_the_consciousness_the_atom

  • Well, now it can be asked why atom has such a goal? Usually goals of substances flow from their substantial forms. If atom leaves the body and is free-floating, then I guess it probably does not have such a goal anymore. That may mean that it underwent substantial change, so there may be no reason to talk about it's temporal identity with anything before leaving the body. Jun 2 '18 at 16:49
  • It may depend on whether an atom has a purpose and is conscious of its direction. If it retains these then a goal will eventually be achieved. Does an atom retain information as to its goal?
    – Jeremy
    Jun 2 '18 at 20:43
  • Well, idea of such atoms is too exotic for me to consider it seriously :D Jun 4 '18 at 19:37

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