John Hood makes a common error when he attempts to make a parallel between brain death and brain life:
It seems to me that the definition of when a person exists can only meaningfully be determined for a large number of people — that is, within a political community that does not necessarily share a particular religious faith — by inverting the clearer definition of when a human person is dead.
We generally identify death as that point when there is no longer any detectable brain activity. The cells of a corpse may still be dividing, and its bodily functions may be sustained for a time by artificial means. But if there is no functioning brain at all, there is no live person anymore.
If we can agree that brain death is the end of a person, then can we not agree that brain function is the beginning of a person?
Hood is not well versed on what brain death is, and he makes a number of errors here. I understand why this argument seems compelling at first glance - but add a little critical thinking and it disintegrates. Here are eight reasons why the parallel between brain death and brain life fails. Note that none of these involves any aspect of religious faith, as Hood seems to imply.
1. Hood assumes that when we declare that someone is brain dead, we are stating that they have lost their human personhood. This is simply false. In fact, according to the uniform determination of death act, which is the legal basis for declaring someone brain dead:
A person may be artificially supported for respiration and circulation after all brain functions cease irreversibly
A brain dead person is still a person, but they are no longer a living person according to this criteria. Strike one.
2. The reason for the above is that a brain dead person has lost the ability to integrate their bodily functions as an organism. The human embryo from the moment of conception has this ability, which is why neuroscientist Maureen Condic argues for the full humanity of the embryo using the same criteria used for brain death. Brain death actually supports that the embryo is a fully functioning living human organism.
3. All brain death criteria state that the cessation of brain function is irreversible. There can never be even a chance that a brain dead individual could recover, lest they would not be dead. On the other hand, the fact that the human embryo functions as an organism without a functioning brain is the opposite of irreversible.
4. Where is the scientific evidence that the metaphysical concept of "personhood" resides in the brain? A question I like to ask: where in the brain is "personhood"? Can I see it on an MRI or CT? Can we transplant the "personhood" section of the brain? If one states that personhood resides in the brain - they have the burden to show where the heck that personhood thing is.
5. I have established that the embryo can integrate its basic organismal functions without a functioning brain, so the presence of a functioning brain in the embryo is more analogous to "higher brain" functioning in adults. If it was the ability to think that gives us personhood, than someone who has lost higher brain function would be considered to have lost their personhood. This is not the case: loss of higher brain function has been repeatedly rejected as a criteria for determining the death of a human being.
6. Brain death criteria is objectively testable, and often needs to be confirmed by a number of different tests (see here). There is no way to objectively test to see whether anyone has obtained "brain life".
7. Historically, the reason why we developed brain death protocols was due to questions that new technologies forced us to ask. We did not necessarily change the definition of death (anyone declared brain dead today would also have been clinically dead in the 1950s), but had to clarify the concept of death due to new challenges. This is not true for "brain life". There has been no new technological advances that would call into question whether or not the human embryo is either human, alive, or an organism. Science is very clear: brain or not, the human embryo is all three.
8. One of the reasons that brain death was defined is the concern that we would be placing human beings during the last moments of their lives in the very unnatural position of having their unintegrated cells being kept alive artificially and unnaturally. This is not a concern for the human embryo - the most natural position for it to be in is in its mother's womb.There are a few more and most of these could use some further explanation, but suffice it to say that the idea that the life of the human person begins at the beginning of brain function has no basis in science and cannot be logically implied from the criteria of brain death.