Discussion Post
In this Discussion Post, you have a choice! You can your initial post about one of the three following thought experiments.
Thought Experiment I: Unintended Replication
"A person dies. Immediately thereafter, the operators of a Replicator program the machine to have a person that they believe would not be a replica of any actual person. But, by an improbably coincidence, the brain and body of the person created in the replicating booth are exact cell-for-cell duplicates of the brain and body of the person who has just died."
(from The Ethics of Killing by Jeff McMahan)
Thought Experiment II: Brain Replacement
"Suppose that I need surgery. All of my brain cells have a defect which, in time, would be fatal. But a surgeon can replace all these cells. He can insert new cells that are exact replicas of the existing cells except that they have no defect. We can distinguish two cases.
"In Case One, the surgeon performs a hundred operations. In each of these, he removes a hundredth part of my brain, and inserts a replica of this part.
"In Case Two, the surgeon follows a different procedure. He first removes all of the parts of my brain, and then inserts all of their replicas.
"The difference between the cases is merely... a difference in the ordering of removals and insertions. In Case One, the surgeon alternates between removing and inserting. In Case Two he does all the removing before all the inserting. Can this be the difference between life and death? Can it be so important, for my survival, whether the new parts are, for a time, joined to the old parts?"
(from The Ethics of Killing by Jeff McMahan)
Thought Experiment III: The Cure
"Imagine that you are twenty years old and are diagnosed with a disease that, if untreated, invariably causes death (though not pain or disability) within five years. There is a treatment that reliably cures the disease but also, as a side effect, causes total retrograde amnesia and radical personality change. Long-term studies of others who have had the treatment show that they almost always go on to have long and happy lives, though these lives are informed by desires and values that differ profoundly from those that the person had prior to treatment. You can therefore reasonably expect that, if you take the treatment, you will live for roughly sixty more years, though the life you will have will be utterly discontinuous with your life as it has been. You will remember nothing of your past and your character and values will be radically altered. Suppose, however, that this can be reliably predicted: that the future you would have between the ages of twenty and eighty if you were to take the treatment would, by itself, be better, as a whole, than your entire life will be if you do not take the treatment.
"Would it be egoistically rational for you to take the treatment? Most of us would at least be skeptical of the wisdom of taking the treatment and many would be deeply opposed to it."
(from The Ethics of Killing by Jeff McMahan)
Choose one thought experiment, and explain it. List and explain each factor relevant to personal identity that this thought experiment controls for and focuses on. What theory of personal identity does this thought experiment seem designed to provide intuitive evidence in support of: the physical theory of personal identity, or the psychological theory?
Now evaluate this thought experiment. Do you think it offers good evidence for the personal identity theory it is designed to support? Why or why not? Are there misleading aspects of this thought experiment that distort our intuitions? Be sure to fully explain and defend your stance.