Thanks. His argument, if I understand it correctly, is an identity argument. Everyone agrees that it is the mind/consciousness that ultimately defines personhood, but pro-lifers think that having a potential mind, or belonging to a species whose nature it is to have a mind, is sufficient to establish personhood. McMahan argues that a mindless organism cannot even have a potential mind, because it does not share an identity with the later organism that has a mind. There is biological continuity between the two, but since mind is dispositive, that biological continuity doesn't count – he rejects "biological personhood." (Normal pro-choice arguments claiming that personhood requires some developmental benchmark can be defeated or at least jeopardized by the Don Marquis argument about deprivation of one's future life. But McMahan's argument is not so susceptible to defeat. It says that an organism without a mind does not have a future with a mind – it says that the identity of an organism with a mind is not a continuation of the identity of the organism without a mind – the two have different identities.) According to McMahan’s embodied mind account, an early embryo has only potential capacity to produce an entity which is non-identical to itself. In McMahan’s view, non-identity of an entity is regarded similarly as; a lump of bronze becomes a statue when it is formed in a certain way, but a lump of bronze and a statue are not identical entities, and the entity, bronze, becomes another kind of entity, a statue, and two different kinds of entities coexist, while they consist of the same material. Similarly, when an early embryo, an organism, comes to possess consciousness function with brain function in the process of growth, it will cause another kind of entity, a person, who is essentially non-identical to itself, existing as different entities in an organism. ( https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=2ahUKEwj14qfy4armAhWqzDgGHcbnAiMQFjACegQIDBAE&url=https%3A%2F%2Fwww.buffalo.edu%2Fcontent%2Fcas%2Fphilosophy%2Fevents%2Feventsarchive%2F_jcr_content%2Fpar%2Fdownload_10%2Ffile.res%2FPANTC%25202014%2520McMahan%2520EmBodied%2520Mind%2520Account%2520and%2520Identity%2520Problem%2520-%2520Minemura.docx&usg=AOvVaw10gK0PeUhokUw8EsZDbs2D ) Since McMahan is a materialist, I suggest pointing out that he should see the distinction between biology and psychology as an artificial one. On a materialistic account, the mind/psyche is nothing but certain patterns of motion of particles that are themselves mindless. There's an unbroken continuum of increasing complexity of movement of molecules right from fertilization till the person turns 25. Sometime thereafter the mind starts slowing down. McMahan is claiming a separation of identities based on a mind-body dualism that he would say he doesn't believe in. Though I said at the outset, "Everyone agrees that it is the mind/consciousness that ultimately defines personhood," I think McMahan should have to admit that a more precise formulation for him would be "It is a certain degree of biological complexity that ultimately defines personhood." And then, since there is no qualitative distinction such as a biological-psychological distinction might suggest, any degree of complexity that he might stipulate will simply be a quantitative benchmark that will be open to the charge that it is arbitrary.
Have you discussed McMahan's "psychological personhood" anywhere? (I don't mean his argument about dogs in your Lesson 5.)
(Normal pro-choice arguments claiming that personhood requires some developmental benchmark can be defeated or at least jeopardized by the Don Marquis argument about deprivation of one's future life. But McMahan's argument is not so susceptible to defeat. It says that an organism without a mind does not have a future with a mind – it says that the identity of an organism with a mind is not a continuation of the identity of the organism without a mind – the two have different identities.)
According to McMahan’s embodied mind account, an early embryo has only potential capacity to produce an entity which is non-identical to itself. In McMahan’s view, non-identity of an entity is regarded similarly as; a lump of bronze becomes a statue when it is formed in a certain way, but a lump of bronze and a statue are not identical entities, and the entity, bronze, becomes another kind of entity, a statue, and two different kinds of entities coexist, while they consist of the same material. Similarly, when an early embryo, an organism, comes to possess consciousness function with brain function in the process of growth, it will cause another kind of entity, a person, who is essentially non-identical to itself, existing as different entities in an organism. ( https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=2ahUKEwj14qfy4armAhWqzDgGHcbnAiMQFjACegQIDBAE&url=https%3A%2F%2Fwww.buffalo.edu%2Fcontent%2Fcas%2Fphilosophy%2Fevents%2Feventsarchive%2F_jcr_content%2Fpar%2Fdownload_10%2Ffile.res%2FPANTC%25202014%2520McMahan%2520EmBodied%2520Mind%2520Account%2520and%2520Identity%2520Problem%2520-%2520Minemura.docx&usg=AOvVaw10gK0PeUhokUw8EsZDbs2D )
Since McMahan is a materialist, I suggest pointing out that he should see the distinction between biology and psychology as an artificial one. On a materialistic account, the mind/psyche is nothing but certain patterns of motion of particles that are themselves mindless. There's an unbroken continuum of increasing complexity of movement of molecules right from fertilization till the person turns 25. Sometime thereafter the mind starts slowing down. McMahan is claiming a separation of identities based on a mind-body dualism that he would say he doesn't believe in.
Though I said at the outset, "Everyone agrees that it is the mind/consciousness that ultimately defines personhood," I think McMahan should have to admit that a more precise formulation for him would be "It is a certain degree of biological complexity that ultimately defines personhood." And then, since there is no qualitative distinction such as a biological-psychological distinction might suggest, any degree of complexity that he might stipulate will simply be a quantitative benchmark that will be open to the charge that it is arbitrary.