Wednesday, November 14, 2007

Materialism and personal identity

It's becoming more and more clear to me that the concept of a person as an entity which is always the agent of personal activity is rationally incompatible with naturalism for personal identity reasons. If naturalism is true, multiple instantiation considerations are just about undeniable, and so computers can be persons. But there really is no way of maintaining a viable concept of persons as well defined entities once we consider the vast array of manipulation that can happen with computing machines. Consider an intelligent system built up as a decentralized swarm of flying, mutually communicating simpler devices exhibiting rational agency collectively but not individually. The idea that there is an entity, a person, under such circumstances is implausible. Think of a community consisting of a number of such swarms which routinely exchange components. Sometimes two swarms fly through each other, and out come two swarms with the member devices being different, and sometimes out comes one bigger swarm. Is there going to be a fact of the matter as to identity conditions?

If I'm right, and if materialism is right, then "personhood happens", but there being a special kind of entity, a person, there where personhood is happening is not going to be a necessary condition for "personhood to happen". I think this conclusion is absurd (for one, it would mean that such a swarm would be wrong if the thought occurred: "I think, therefore I am"), and so materialism is false.

But suppose we don't think the conclusion absurd. Would it make sense to say that there is such a thing as a person in our own case? Or should we still then say that "personhood happens"? I suspect the latter, unless we just identify the "person" with the animal in whom personhood happens. But the latter isn't going to be that plausible, I think, once we realize that one and the same animal brain could in principle, by parallel processing, support more than one stream of rational agency.

If all this is right--and there are a lot of promissory notes here--then if materialism is true, there are no persons, and hence I do not exist.


Martin Cooke said...

Hi; I tend to agree... but it's very easy for some of us to attribute personhood to a teddy bear (and personality to a computer, etc.), and the fact that a teddy bear is a connected solid object doesn't count in favour of it being a person... so maybe some of us will have no greater problem with the swarm of robots, than they do with brains of neurones.

Incidentally, I'm also unsure why the swarm would be wrong to think "I think, therefore I am." The swarm is, after all; and if it does think that then it is also a swarm that is connected enough to have such a singular thought... And one problem with our own case (that's puzzled me for years) is the split-brain patients who seem to some of us to be two persons, intuitively (more clearly than an imagined swarm of robots seems to be anything really).

Johnny-Dee said...

Hey Alex, I'm a long-time reader, but I don't think I've communicated with you before. I've always found your philosophical blogging intellectually invigorating, and I'm glad that I've finally found an excuse to post a comment. I think the basic thesis of this post is correct. I had reached the conclusion that naturalism is incompatible with robust personal identity when I read the early works of Peter Unger, especially about the problem of the many as well as his short little piece, "I do not exist." I'm sure you are familiar with these arguments, and I was wondering if you think these problems with personal identity are genuine problems for all forms of naturalism. It looks like your argument bears some kinship with some of Unger's. Am I correct in this judgment?

Vlastimil Vohánka said...


How - exactly - would your thoughts apply to the following aggregate theory of human persons by Quentin Smith? Thanks.

Q. Smith, „Internal and External Causal Explanations of the Universe“:

"A mereological sum is similar to a set in that it essentially contains all and only the members it actually contains. An aggregate, however, does not contain all its members essentially. A human being is an aggregate, but if I lose one of my skin cells I remain the same aggregate. The Earth is also an aggregate and remains the same if one of its parts is lost (by being sent into outer space in a rocket). An aggregate's identity is not determined by enumerating its parts but instead by a certain property of the aggregate itself. The Earth, for example, is that aggregate which uniquely possesses the property being the third planet from the sun. Suppose the universe is an aggregate. (For an argument that the universe is an aggregate, see (Smith, 1986, Felt Meanings of the Universe: 200-210; 296-301)). ... the universe is the aggregate defined by the property, being composed of whatever causally connected physical states there are."

Alexander R Pruss said...


The problem is that the swarms in my thought experiment are capable of so much interchange of particles that it doesn't make much sense to talk of their identity over time, and the problem of distinguishing which flying bits are in the swarm and which aren't is a particularly serious one, because what mental states belong to the swarm will depend in part on which flying bits one counts as part of the swarm. (Think of some outliers that communicate less effectively with the rest of the swarm.)

One might conclude that any way of reaggregating the bits of swarm is a person, and hence if there are N devices flying in the swarm, the swarm as a whole has somewhat less than 2^N personhoods (somewhat less, because some combinations don't make up a person, for instance because they don't have enough pieces).


I think Smith says what Unger is criticizing. There are many aggregates of particles roughly where I am. Some have a few more and some have a few less. Which am I?

In any case, Smith's move is not going to help get out of the problem in the case of swarms.


Well, here's how I'd try to get out of Unger's argument if I were a materialist. Despite materialism, it's a mistake to focus on the physical substrate too much--we could replace the brain by a computer, piece by piece, and survive. What matters is the stream of thought and action. Now, we don't want to identify ourselves with that stream, since that would probably have the wrong modal properties (if we are a particular stream of thought and action, and we couldn't have acted otherwise). But we want something close to that. So we should identify ourselves with the body as subject of that stream. Our criteria of identity will then be psychological. The Unger argument then shows that there is no fact of the matter as to which pieces of matter constitute us. But that's OK. We're not identical to the bits of matter or to aggregates of them, but rather we are constituted by them, and we can allow that to be vague, since what really matters are the mental states, and those are no different if we take a particle more or less.

What's neat about some of the more science-fictional examples, though, is that the bits of swarm and the like matter mentally to the swarm as a whole.

Ilíon said...

"If all this is right ... then if materialism is true, there are no persons, and hence I do not exist."

I (a simple no-one, alas) came to this realizaton a year and half or so ago. What I mean is that I wasn't consciously trying to solve this problem, but like a cartoon light-bulb-idea, the realization came to me one day.

I've been trying, off and on since then, to see how new or unique the idea is.

Victor Reppert said...

One of my arguments in C. S. Lewis's Dangerous Idea is the argument from the unity of consciousness. The idea is that if there is no unified consciousness (and materialism seems to imply this) then there is no one individual person who thinks the premises and thinks the conclusion in a rational inference.

Ilíon said...

VR: "... then there is no one individual person who ..."


Or, consider the point from a slightly different angle: If 'materialism/naturalism/physicalism' is the truth about the nature of reality, then not only is 'consciousness' and/or 'mind' an "illusion" (of whom, exactly, one always wonders; hence the scare-quotes), but even the fact/existence of the physical body (human or otherwise) is an illusion (again, of whom?).

If 'materialism/naturalism/physicalism' is the truth about the nature of reality, then a lifeless and insentient rock *may* exist, for a time, but no living thing actually exists, ever ('living' used here in the sense of 'biology').

This is because -- and regardless of the truth-status of 'm/n/p' -- living things have no physical/material continuity from one moment to the next: the matter of which living entities are composed is in constant flux; not only are individual cells (of "higher" organisms) being constantly created and/or killed, but the the matter of which those cells are made is constantly being add-to and subracted-from.

If you *are* the matter of which you are made -- if the fact of you is fully explained-without-remainder by reference to chemicals and chemical reactions -- then you simply cannot exist continuously (unitarily) from one instant to the next. One might as well speak of an explosion as a thing which exists.

And yet, the truth of the matter is that living entities, even individual cells, have identity, but non-living things do not.