Photo Credit Viviana Rishe on Unsplash
Psychological approaches to personal identity are normally used to argue that since an embryo doesn’t have a psychology (doesn’t have a mind), it doesn’t have a continuous identity with more highly-developed, “smarter”, stages of the organism that will follow the embryo stage; and that therefore if you kill an embryo, you don’t deprive it of the experience of any highly-developed stage of life. To have a right to life, it is not enough, they say, just to be human.
“Psychological-personhood” approaches go on to say that more cognitively-developed stages of the human organism constitute a person, while the less-developed stages do not (the organism is a non-person human, apparently).
I am quite willing to accept a psychological approach to personal identity, but I think in order to be valid, it would have to recognize not only subjective phenomena of the mind (memories, for instance, are often emphasized by such approaches to identity), but also the physical particles and physical forces that presumably constitute the substrate of those phenomena:
1. All psychological phenomena and activities, including subjective experiences, are generally presumed by scientists to emerge from the objective molecular activity of the brain. The molecular activity is primary, the substrate.
2. Since it is primary, if we’re going to talk about psychological connection/continuity, the related physical molecules will be the factor most relevant to that connection/continuity.
3. While my present brain may or may not still have any of the same molecules that were present at my organism’s zygote stage, there is definitely connection/continuity between molecules present then and the molecules present now. If this is correct, as I think it is, it is enough just to be human. (To make this more readily graspable, and a stronger-sounding argument, we could say “between molecules present in the earliest embryonic structures that can be scientifically identified as precursors of the brain, and the molecules present now”, and still include all but the earliest embryos.) The exact molecules and molecular activity in my brain now could not be there without a straight line from certain exact molecules and molecular activity present at my zygote stage – definitely a connection.
4. Molecular activity being primary, realities of molecular activity will likely nudge us more toward the most correct possible intuition about connection / lack of connection than will realities on more subjective psychological levels.
I have found at least one credentialed philosopher who seems to agree with this idea. Alexander Pruss has written:
And there is a further objection [to the idea that I am a brain]. My brain developed out of earlier cells guided by the genetic information [in DNA] already present in the embryo. There was, first, a neural tube, and earlier there were precursors to that. Brain development was gradual, cells specializing more and more and arranging themselves. At which point did I come to exist? And why should the cells that were the precursors of the brain cells not be counted as having been the same organ as the brain, albeit in inchoate form? If so, then perhaps I was there from conception, even on this view.
I mentioned that to make my above argument sound stronger, instead of saying “between molecules present then [at the zygote stage] and the molecules present now,” we could say “between molecules present in the earliest embryonic structures that can be scientifically identified as precursors of the brain, and the molecules present now”, and still include all but the earliest embryos. But I think that even at the zygote stage there must be certain molecules which, under the guidance of that zygote’s Homo sapiens DNA, are playing a role that is essential to the development of the fully-developed human brain, the brain that “composes the music of reason, the poetry of emotion, and the symphony of consciousness” (Diane Ackerman) – and thus should be considered the first stage of that brain.
The argument I have offered here rests partly on prioritizing a perception of the mind as the physical substrate of the mind, over a perception of it as the subjective phenomena that emerge from that substrate. But that prioritizing is very defensible, it seems to me. Perceiving the mind as its subjective phenomena is an anthropomorphized view instilled in us largely by the constraints of evolutionary adaptiveness: that is, we evolved so as best to survive, not so as best to see truth; and the truth is that the physical substrate of the mind is primary, and the subjective phenomena secondary.
Philosopher Daniel Dennett and others call the anthropomorphized view the “manifest image”. As those philosophers and many others recognize, philosophy should not exclude a physics-oriented, naturalistic, outlook. Philosophers should never limit themselves to the “manifest image”.