Introduction
Some philosophical problems can be solved with very little philosophy. Whether a person could migrate from one body to another is one such problem. While this problem might initially strike us as profoundly philosophical, it actually admits a neat, realistic solution. Neat, because the success of the solution turns on few controversial philosophical theses. Realistic, because it’s given in the form of a scientifically sound procedure. Throughout this article, I will use the term ‘migration’ to mean the transfer of a person across bodies.
The Philosophical Provisos
Although my case requires minimal substantive philosophy, two philosophical provisos are required to regiment the terms.
Proviso 1: A person’s body is a physical object that constitutes a human life and is (or was) intimately related to that person.
By ‘constitutes a human life’, I mean that it has the characteristics of life (e.g. homeostasis, growth and response to stimuli) appropriate for a human being. A person’s body doesn’t have to be conscious or self-reliant to be alive in this sense (e.g. people who are in a coma or rely on an artificial organ have bodies).
By ‘intimately related to that person’, I mean something like being co-located with, being the grounds for, being the physical medium of experience for, or constituting that person. Since my argument goes through on any of these disjuncts, I will not settle on any particular one to avoid unnecessary philosophical controversy.
Proviso 2: If a person’s first-person experience is uninterrupted throughout a change, then they persist through that change.
Here, an experience is uninterrupted if and only if it is psychologically and locationally continuous. Importantly, Proviso 2 is not a biconditional, identity criterion, or theory of identity. As such, it is silent on teletransportation cases, which challenge the notion that identity requires the continuity of location. Moreover, it takes no stance on the animalist claim that identity can persist without psychological continuity. Instead, it merely states a basic datum that theories of identity ought to accommodate.
The Practical Procedure
The objective of the procedure below is to transplant a person (P) from their body into the body of a donor (D). The operation is roughly a brain transplant, as it involves P’s brain being moved from P’s body to D’s. However, it differs from most brain transplant scenarios in two crucial ways. First, to respect Proviso 1, D’s body is kept biologically alive during the operation by being placed on a ventilator. This ensures that P is being transplanted into D’s body, and not into a heap of bones, flesh and organs that only used to be D’s body. Second, to respect Proviso 2, P’s experience is uninterrupted throughout the operation. These are accomplished through the following steps:
1. Move P’s body next to D’s body, keeping both alive in the biological sense.
2. Sever the nerves connecting P’s brain to P’s ears, then reconnect them to D’s ears.
3. During Step 2, P watches a silent film so that the experience is uninterrupted.
4. Sever the nerves connecting P’s brain to P’s eyes, then reconnect them to D’s eyes.
5. During Step 4, P listens to music, again so that the experience is uninterrupted.
6. Sever the nerves connecting P’s brain to P’s arms, then reconnect them to D’s arms.
… and so on, until P’s brain is fully connected to D’s body.
By dividing the transplant into multiple steps, we ensure P maintains an uninterrupted experience through different sensory organs, guaranteeing the continuity of personal identity provided by Proviso 2.
Moreover, it secures the operation’s scientific viability. For example, in 2023, NYU Langone Health performed a full-eye transplant using stem cells to reconnect severed nerves. Similar technology could be used for ears, arms, etc. We also have the technology to keep a body alive (in the biological sense) without a brain. For example, Jahi McMath was kept on a ventilator for almost a month after she was brain dead. During this time, her body was still hers, given Proviso 1. Hence, unlike most other hypothetical transplant cases, the procedure in this one is scientifically sound and faces no profound practical challenges. Specifically, it is possible in a nomological and technological sense, meaning that it is accomplished in nearby possible worlds that resemble our world in natural laws and technological capabilities.
‘If a person’s first-person experience is uninterrupted throughout a change, then they persist through that change.’
Objections and Replies
First, one might object that a (living) human body is essentially a person. Therefore, even if D’s brain is detached from their body, the person D still exists in virtue of their body’s continued life. So after the transplant, person D regains consciousness with P’s brain and mental states, while person P ceases to exist.
However, this account of the transplant relies on an implausible notion of what a person is. It entails, among other things, that a person can exist as a brainless body and that a person can cease to exist during an uninterrupted first-person experience. These claims appear blatantly false. However, I should note that they are endorsed by certain radical animalists who identify the person with the (living) body. In response, I argue that this is simply evidence against radical animalism. Animalists should opt for milder positions, such as the view that we aren’t essentially persons or that person is a phase sortal.
Now, let’s consider the objection that the brain is an essential organ in the human body, so once D’s brain is severed from the rest of D’s body, what remains of D’s body ceases to be a body at all. Hence, instead of migrating into D’s body, P actually migrated into a pile of flesh that used to be D’s body.
While the first account relies on an implausible notion of a person, this account relies on an implausible notion of a body. To begin, the brain as a part of the body is a physical entity, so this view must defend the specialness of the brain as a physical object relative to other non-essential organs. One might highlight the brain’s role in integrating bodily functions. However, this role is actually served by the brainstem, which is irrelevant for personhood-constituting mental states (such as consciousness), meaning that we can simply transplant the rest of P’s brain to migrate P. Moreover, even if the brain plays such a key role, it still wouldn’t be essential to the body unless it’s also essential for biological survival, as a body is characterized in biological terms. From the McMath case, we know that the brain is not essential in this sense.
‘The objective of the procedure below is to transplant a person (P) from their body into the body of a donor (D). The operation is roughly a brain transplant, as it involves P’s brain being moved from P’s body to D’s.’
Conclusion
In his Blue Book, Wittgenstein famously warned of the philosopher’s ‘craving for generality’. Heeding this warning, I adopted an approach based on lightweight philosophical provisos and a realistic case rather than ploughing through the personal identity literature. Hence, this article is deflationary in the sense that it involves little speculative modal epistemology and philosophical heavy lifting. Nonetheless, it supplies a substantive answer to the question of migration: because it is nomologically and technologically possible for a person to migrate between bodies, a person could (in this sense) migrate from one human body to another.
