Physicalism, Property Dualism, and Personal Identity


I have been thinking about physicalist/property dualist accounts of personal identity, including the memory account especially. The memory account says that personal identity is grounded in the continuity of memory in a single subject throughout time. So long as your current brain has the same memories as time progresses, it can be considered numerically the same person that existed previously as you in the past.

Here I will attempt to offer a critique of this theory of personal identity. As far as I know, this material is all original, but if I have mistakenly started regurgitating something Swinburne said (maybe something I read once and forgot where it came from–you know how that goes), please correct me and give me a chance to apologize.

One thing that strikes me as initially implausible about this account is that the brain has a cycle where it replaces every cell inside itself with new ones. Now, because of this, we obviously can’t locate personal identity in the continuity of a material object’s existence. But I think this fact about the brain also challenges the memory account of personal identity. Lets take what I consider to be the most sophisticated account of something-remotely-physicalist: epiphenomenalist property dualism. Property dualism says there is no immaterial substantial center of consciousness (soul) seperate from the body. Nevertheless, there are mental properties that are not physical properties. Your thoughts are not entirely reducible to physical objects; they have non-physical properties that genuinely transcend matter. Epiphenomenalism identifies mental entities as emergent properties or states that come into existence when the brain is in a certain state.

Now on epiphenomenalism, as I understand it, there is a necessary correlation between physical states and mental properties. A mental property will exist only when a certain combination of physical objects exists in a certain location. What this means is that there is no incorruptible mental life that is beyond the possibility of destruction. Rather, there is the possibility that a person’s consciousness will become destroyed if the physical objects that give rise to it get displaced or destroyed.

Now think about that with relation to certain beliefs which would constitute memory. Your belief that “I was born in a hospital” is a token of a certain belief-type. What that means is that there are more than one beliefs that “I was born in a hospital”. The belief-type “I was born in a hospital” is like the image on a strip of film that has been replicated; it can look exactly the same as other images on other strips of film. For instance if a movie was being mass-produced on vhs for home theater, there would be many versions of the movie, each with their own pieces of film, all looking more-or-less exactly the same.

This would be comparable to your belief “I was born in a hospital”; billions of other people have had this same kind of belief before. There have been many different belief-tokens of this belief-type. So what makes these belief-tokens different on the epiphenomenalist account? They were all produced from different physical locations by different brains. The same kinds of particles that gave rise to a belief-token x1 of type X gave rise to another belief x2 in a different brain. Yet these two tokens x1 and x2 are different precisely because they arose from a different arrangement of material objects. Here’s the thing: if the matter in your brain is being replaced frequently, then it seems that different combinations of matter are producing your beliefs over the years. At one point in your life, combo-token z1 of type Z was producing belief-token x1 of type X. Later, combo-token z2 was producing belief-token x2 of type X. All the matter that gave rise to your first belief has been replaced now. And because different combinations of matter are producing your belief you now hold, we can legitimately say you have a different belief-token.

This seems to undercut the possibility of a continuity of personal identity given epiphenomenalism or pretty much any physicalist or property-dualist account of personal identity. After all, your beliefs *are not the same as they were before*. What was once your belief that “I was born in a hospital” is now a different version–a new token of the same type of belief. If this is true, then we don’t seem to be dealing with the same beliefs that constitute memory; hence it is hard to see how we could be dealing with the same person enduring throughout time if we base personal identity off of memory.

What about just saying that its the type, not the token, that matters in order to retain identical memories? After all, if you still believe “I was born in a hospital”, what does it matter? Here we run into some problems. For think of the analogy with tv again. Lets say there’s a VCR that is your brain, the tape is a brain state, and the images on the tv are the mental states that arise from having the brain state in your brain. If I take a tape of Boodock Saints and put it in, and the tv has a picture of a scene from Boondock Saints, then this parallels what happens when you have a mental state of a certain kind for the very first time emerge from your brain. But lets say that one copy of Boondock Saints gets trashed; this would be comparable to your brain state losing the original physical particles that caused your belief. You would not have the image on the tv that came from the tape anymore; similarly you would not have the belief that came from the brain state anymore. Now lets say we replace the old Boondock Saints tape with a new one of the same kind–a second copy of Boondock Saints–and stick it in the VCR. What would this be the equivalent of for personal identity? It is the same as the lost group of particles being replaced by particles of the same kind in the same kind of relations, so that they give rise to the same type of belief.

But something is fishy here. When we replaced the tape, we don’t have two identical tapes, one that was replaced which is exactly the same as the one that is the replacement. There is not a strict continuity of identity here. When the image of Il Duce with guns blazing pops up on the screen, therefore, it may look exactly the same as the first image that was playing from the original tape; but it is *not* the same. Its a different tape. Likewise, when we replace the brain state with a new brain state of the same kind, it looks like we’re dealing with the same belief; but we’re not. There’s no strict continuity of identity there. If we aren’t willing to say that there is an absolute continuity of identity for the image of Il Duce when we put in a copy of the same tape, then we can’t say we’ve got an absolute continuity of personal identity in memories of the same kind arising from different sets of the same matter.

An alternate way of looking at personal identity is to see it as a basic and unanalyzable notion that is grounded in the uniqueness and distinctness of a person from his or her body. This I find to be the preferable route. Because our intuitions about the absolute continuity of our personal identity throughout time should not be taken lightly, perhaps we ought to accept the mystery and uniqueness of persons without reducing them to a kind or an effect of physical existence.


4 Responses to “Physicalism, Property Dualism, and Personal Identity”

  1. Alexander Says:

    I responded to this in a new entry on my blog.

  2. Derek Says:

    MG, Great post. My senior thesis was on personal identity, specifically on what would do the work of grounding the metaphysical “uniqueness of persons.” I do believe the single most powerful argument for (substance) dualism is the phenomenon of the continuity of persons. Like you argue, when I look at a photograph of when I was twelve and say (truly) that “this is a picture of me,” materialism is in trouble: the physical object represented by the picture no longer exists, and therefore, if that picture is a picture of me, I must be something non-physical. Although I do think this argument shows how dualism has resources (and therefore is explanatorily more plausible) than materialism, there’s still some major work to be done for the dualist. Consider, for example, that I am identical to my soul, where the word soul denotes the following object:Soul = the entity which houses the following capacities: reason, deliberation, intentional action, love, consciousness, etc. Even if we define the soul in this rather robust way, we still aren’t out of the woods in explaining why I am this particular soul, and not another. For instance, even though I am identical to my soul, what is it about my particular soul that makes me identical to it and not, say, your soul. Presumably, you have (are) a soul. But everything essential to your soul is also essential to mine. You soul is comprised of the same capacities my soul has, and that’s what makes it a soul. One plausible theory which explains why I am this particular soul and not another is either some assay of bare particularity or haecceitism (bare particulars/haecceities are the substratum/causal power which individuates the properties (universals) it has. As such, the reason why I am this particular soul and not your soul is because my soul is individuated by a bare particular or haecceity. In my senior thesis, though, I argued that this construal does provide a theory for the causal power of individuation, but is still explanatorily bankrupt in showing why I am me and not you. Instead of showing why I am me and not you, it merely shows how, causally speaking, souls get individuated. I went on to argue that a theory that would do the work of showing not just how, but why, is the following. The reason why you and I cannot swap souls is because my soul is individuated not just by a bare particular, but a particular quality (in the non-universal sense) which I am. This quality is what individuates my soul, causally speaking, as well as gives my entire being a unique qualitative distinctness which necessarily cannot be multiply instantiated.

  3. MG Says:

    Derek–Thanks for the comments.What you have said about souls being individuated such that they can’t be switched in the final account you mentioned (the one you argued in your senior thesis) is both interesting and similar to conclusions I have come to recently about personhood.In your final analysis, what do you mean by “quality”?

  4. Derek Says:

    In your final analysis, what do you mean by “quality”?The problem of universals and particulars:Universals (suchness)- the entities (properties, qualities, characters, types, natural kinds) which are multiply instantiated (e.g., the book sitting in front of me and my shirt are both colored red- the redness is the a universal which is multiply instantiated). ‘Particulars (thisness)- the entity which either cannot be multiply instantiated, or, the causal power that makes something identical to itself. The traditional view is that no thing is both a particular and a quality, because any quality is multiply instantiated (qualities are universals). When it comes to personal identity, though, I deny this claim. My view is that I am a this-such. I say it is a “such” because it is qualitative- you can distinguish my essential quality from other qualities; but unlike other qualities (e.g. being funny, being born to so and so, writing this sentence right now, etc.), it is not possible for my essential quality to be instantiated in anything else; that is, it’s essentially always a “thisness.” Basically, I have an essential quality (call it Derekness or Derekeity) which you would be acquainted with if you knew me. It’s a simple quality; it has no constituent parts and it cannot be described in more simple terms. Much like the color red, for instance. There’s no way to describe red, but that doesn’t mean we have no knowledge of red. It just so happens that it’s a simple entity, and you know it via being acquainted with it. Unlike the quality of red, however, Derekeity is much more ‘flavorful’ (it’s more than just a color). In developing my view I received the most help from the following sources:Robert Adams “Primitive Thisness and Primitive Identity” (I am, on his view, an “extreme haecceitist”)Alvin Plantinga, “The Boethian Compromise” and chapters 4-6 of The Nature of NecessitySaul Kripke, Naming and Necessity

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