What follows is a brief discussion about Parfit's
We Are Not Human Beings, and my thinking on the topic. As per other such discussions on this blog, it isn't necessarily intended to be a robust interpretation or set of arguments, rather a handy overview and part set of handy notes primarily for my benefit, but also hopefully for the benefit of others.
Partfit, D. (2012). We Are Not Human Beings.
Philosophy, the Journal of the Royal Institute of Philosophy, volume 87, number 339, January 2012.
Parfit discusses personal identity; what it is that is
us, how it can be distinguished from things that are not
us, and how we should think about ourselves. There are numerically identical things; my keyboard has been the
same keyboard for several years. Here by same I mean it is the same object, and a spatial-temporal path could be traced for it, and we could be confident that when viewed in the past it is identical in the sense that it is the same object. Things can also be considered qualitatively identical. My preferred design of trackball sadly only lasts a few years before wearing out, so over the years I have had several objects that share a whole host of properties (they are the same model, colour, etc.) but are different objects. The trackball that I have now is the same sort of trackball that I had ten years ago, and aside from the serial number it is indistinguishable to me, but it isn't the same object. The numerical identity of my trackball is of no concern of me, I only care if I have a qualitatively identical trackball.
People are different. We are concerned with numerical identity as well as qualitative identity. Substituting my beloved with her twin simply wouldn't do.
Or would it?
What we are interested in with regards to personal identity is the thinking bit of a person. If we swapped two people's brains over we would consider it a body transplant rather than a brain transplant. We would follow the brain if we were concerned with things like responsibilities, promises, guilt, and friendship.
Parfit covers three concepts of personal identity; the soul view (which he promptly sets aside), the Animalist View, and the Lockean View. The Animalist View is rooted in our identity as animals, it is biological continuity that is of interest to us. This certainly seems to be the face value working rule that we use; we identify persons based on their bodies. The Lockean View is focused on psychological continuity, and Parfit gives us his definition:
The Narrow, Brain-Based Criterion: If some future person would be uniquely psychologically continuous with me as I am now, and this continuity would have its normal cause, enough of the same brain, this person would be me. If some future person would neither be uniquely psychologically continuous with me as I am now, nor have enough of the same brain, this person would not be me. In all other cases, there would be no answer to the question whether some future person would be me. But there would be nothing that we did not know.
Parfit presents a continuum of thought experiments to draw out the distinction between the Animalist and Lockean views, moving along the scale; Transplanted Head, Surviving Head, Surviving Cerebellum.
Parfit refers to McMahan's
Embodied Part View. Under this view we are the thinking part of the Human Animal. Parfit extends this view with the
Embodied Person View; human animals think by having a concious thinking part which is a person in a Lockean sense.
Parfit covers a number of potential and actual objections, but ends with the conclusion that we can be best described as Embodied Persons; "Since the animal thinks only by having a part that thinks, there are not too many thinkers here [the Too Many Thinkers objection]. And since the animal is a person only in the derivative sense of having a Lockean person as a part, there are not too many persons here [the Too Many Persons objection]".
It would seem to me that there is another distinction here. The thinking parts in our brains is the embodied part of us, the apparatus and substrate of thinking, of our identity. Our identity however is the brain-state. Admittedly our identity, our thinking, is tightly coupled with the physical mechanisms of the thinking which are in turn tightly coupled with wider aspects of our bodies. If my brain was reset to a blank state, then there would be a break in the psychologically continuity. It may be that the brain state left is the closest to generating my identity of any brain in existence, but if we were to say it is still me we would merely be making the best of a bad situation.
- If my brain state was destroyed/reset, would we still claim identity? Possibly, but only in so far as we conflate personal identity with our physical shells.
- If 100 people had their brain state reset, and their physical appearance altered so that they all appeared the same... would we consider there to be anything of personal identity left to trace? No.
- If my brain state was destructively copied (i.e. moved) into a replicant of me, we would consider my identity to be in the replicant.
- If my brain state was destructively copied into a computer that functionally simulated my brain for me, and then moved back into my original body we consider the human-body-brain-state-copy to be me.
Our personal identity is the thinking itself, the representation stored and manipulated in the brain. The apparatus for personal identity that we have available to us is the parts of the brain that do the thinking, which are embodied in the human animal. In computer terms we aren't even the software, we're the current state of the software at a moment in time.
Numerical identity isn't important. Qualitative identity is what matters; we're interested in the properties of a thinking animal/other. In a not quite fleshed out analogy, in the arrangement of physical things so that the rainbow twinkles just so, we are the rainbow.
The Cogito—I think, therefore I am—becomes:
Thinking occurs, I am the thinking.
