A thought experiment akin to the one that you propose has been deployed by Derek Parfit, in his classic book, Reasons and Persons , which I highly recommend if you're interested in this topic, in order to argue that personal identity is "not what matters." According to Parfit--I'm simplifying somewhat--if some agent has a perfect duplicate who is psychologically continuous with the agent, then, according to Parfit, even if the agent dies, and therefore the agent's consciousness does not continue, and so s/he does not continue to exist (Parfit is therefore answering question to the negative, and admitting that you won't survive) what's important, namely one's plans, projects, etc., will be continued by the agent's duplicate, and that, again according to Parfit, is more important than the survival of one's consciousness--indeed, in such a case, one shouldn't be worried about dying, because what one values will be carried on (albeit only by a psychologically continuous duplicate of oneself). Now Parfit...

Your question goes to the heart of debates about personal identity, and even goes back to the early modern starting point for those debates, the chapter on personal identity in John Locke's Essay Concerning Human Understanding . Much discussion about personal identity has turned on the question of whether personal identity is to be located in psychological continuity or in bodily continuity of some sort; if one is inclined to think that the identity of a person is to be identified with the identity of her brain, then personal identity does indeed seem to consist in bodily continuity. Your question goes even further, for you wonder whether the brain is to be identified as the locus of personhood, so that a person just is her brain. One thing that this view has going for it is that it seems that all human persons have had--it's not clear whether we can know, without doing brain scans, that all human persons have brains--brains. So having a brain would seem to be necessary for being a...

This is a deep and interesting question, which goes to the heart of the topic of personal identity, and reflects a tradition that stretches back to John Locke's treatment of the topic in the Essay Concerning Human Understanding . A preliminary note is in order, however: most contemporary treatments of personal identity--and that of Locke as well--do not turn on whether personal identity is determined by the body (one's 'physical appearance') or the soul, but in terms of whether personal identity is determined by the identity of the body or the mind. (By framing the question in this way, philosophers who are agnostic about the existence of the soul, or thinking substance--like Locke--or who deny its existence--like many participants in recent philosophical debates on the topic, can engage it without having to take up the issue of whether there is such thing as a soul.) Interestingly enough, the kind of 'thought experiment' that you propose to illustrate your question is one that Locke himself...

The idea of the self that is called into question when it is claimed that the self is an illusion is the idea of a substantial, persisting, intellectual substance, such as the self of which Descartes, in the second of the Meditations on First Philosophy , claimed to have knowledge, and which the later Rationalist, G. W. Leibniz, took as one of the foundations of his philosophy. One of the most famous Western challenges to such an idea is raised by David Hume, in A Treatise of Human Nature . In Book 1, Part 4, Chapter 6 of the Treatise , "Of Personal Identity," Hume characterizes the belief in a persisting self: "There are some philosophers, who imagine we are every moment intimately conscious of what we call our SELF, that we feel its existence and its continuance in existence; and are certain, beyond the evidence of a demonstration, both of its perfect identity and simplicity." To this view, Hume responds: "For my part, when I enter most intimately into what I call myself , I...

The answer to this question depends on what one's criteria for personal identity are, as well as the nature of the changes in personality brought about by the envisioned brain manipulation. If, for example, one took personal identity to consist in psychological continuity, understood to consist in a continuation of interests, plans, projects, etc., then if one were to alter someone's brain and that person's personality were to change markedly enough that the person no longer shared the same interests, plans, projects with the person who entered the operating room, than the person would indeed have ceased to exist, as a result of the operation, and so one could be said to have effectively killed the old person in the operating room and caused a new person to be born. If, however, one takes identity to consist in bodily identity, then even in a case when a person's interests, plans, projects, etc., were to change markedly, provided that the person continued to occupy the same body, then the same person...