Must-Read: Adam Elga: Defeating Dr. Evil with Self-Locating Belief: "Safe in an impregnable battlestation on the moon, Dr. Evil had planned to launch a bomb that would destroy the Earth...
...In response, the Philosophy Defense Force (PDF) sent Dr. Evil the following message:
(Forgive the impersonal nature of this communication—our purpose prevents us from addressing you by name.) We have just created a duplicate of Dr. Evil. The duplicate—call him “Dup”—is inhabiting a replica of Dr. Evil’s battlestation that we have installed in our skepticism lab. At each moment Dup has experiences indistinguishable from those of Dr. Evil. For example, at this moment both Dr. Evil and Dup are reading this message.
We are in control of Dup’s environment. If in the next ten minutes Dup performs actions that correspond to deactivating the battlestation and surrendering, we will treat him well. Otherwise we will torture him.
Best regards, The PDF
Dr. Evil knows that the PDF never issues false or misleading messages. Should he surrender? Whether Dr. Evil ought to surrender depends on whether he ought to remain certain that he is Dr. Evil once he reads the message.... I will argue that only the first of the two lines of reasoning is correct, and that after Dr. Evil receives the message he ought to have exactly the same degree of belief that he is Dr. Evil as that he is Dup.... Dr. Evil ought to surrender to avoid the risk of torture...