Die meisten der alten Philosophen haben sich durch eine große Anzahl von Interessen ausgezeichnet und durch ein beeindruckendes Wissen auf den meisten ihrer Interessengebiete. John Locke, den viele wegen seiner politischen Philosophie kennen, hat sich u.a. für Astronomie und Mathematik interessiert und daneben eine ganz eigene Identitätslehre entworfen, die man als erste Form von Sozialpsychologie ansehen kann.
Die Ausgangsfrage, mit der Locke seine Überlegungen startet, lautet: Ist der 30jährige John Locke derselbe John Locke, der er als einjähriger war?
“One way of approaching the question about what makes a human being the same person over time would be to point out that we are living beings. You are the same individual animal that you were as a baby. Locke used the word ‘man’ (…) to refer to ‘human animal’. He thought it was true to say that over a life each of us remains the same being that develops in the course of its life. But for Locke being the same ‘man’ was very different from being the same person.
According to Locke, I could be the same ‘man’, but not the same person I was previously. What makes us the same person over time, Locke claimed, is our consciousness, our awareness of our own selves. What you can’t remember isn’t part of you as a person. To illustrate this he imagined a prince waking up with a cobbler’s memories; and a cobbler with a prince’s memories. The prince wakes up as usual in his palace, and to outside appearance is the same person he was when he went to sleep. But because he has the Cobbler’s memories instead of his own, he feels that he is the cobbler. Bodily continuity doesn’t decide the issue. What matters in questions about personal identity is psychological continuity. If you have the prince’s memories, then you are the prince. If you have the cobbler’s memories, you are the cobbler, even if you have the body of a prince. If the cobbler had committed a crime, it would be the one with the prince’s body that we should hold responsible for it.
Of course, in ordinary cases memory doesn’t switch like that. Locke was using this thought experiment to make a point. But some people do claim that it is possible that more than one person can inhibit a single body. That is a condition known as multiple personality disorder, where it appears that different personalities a present within a single individual. Locke anticipated this possibility and imagined two completely independent persons living in one body – one present by day, the other only at night. If these two minds have no access to each other, then they are two persons, on Locke’s account.
For Locke, questions of personal identity were closely connected with moral responsibility. He believed that God would only punish people for crimes they remembered committing. Someone who no longer remembered doing evil wouldn’t be the same person who committed the crime. In everyday life, of course, people lie about what they remember. So if someone claims to have forgotten what they’ve done, judges are reluctant to let them off. But because God knows everything, he will be able to tell who deserves punishment and who doesn’t. A consequence of Locke’s view would be that if Nazi-hunters track down an old man who in his youth had been a concentration camp guard, the old man should only be held responsible for what he can remember, and not for any other crimes. God wouldn’t punish him for actions he’d forgotten about, even if ordinary courts wouldn’t give him the benefit of the doubt.
Locke’s approach to personal identity also gave an answer to a question that vexed some of his contemporaries. They worried about whether you needed the same body to be brought back to life in order go to heaven. If you did, what would happen if your body had been eaten by a cannibal or a wild animal? How would you get all the body parts back together to be raised from the dead? If the cannibal had eaten you, then bits of you would have become part of him or her. So how could both the cannibal and the cannibal’s meal (i.e. you) both be restored as bodies. Locke made clear that what mattered was that you were the same person in the afterlife rather than the same body. On his view you could be the same person if you had the same memories, even if these were attached to a different body.
One consequence of Locke’s view is that you probably aren’t the same person as the baby in the photograph. You are the same individual, but unless you can remember being a baby, you can’t be the same person. Your personal identity only extents as far back as your memory. As your memories fade in old age, too, the extent of what you are as a person will also shrink.
Warburton, Nigel (2012). A Little History of Philosophy. Yale: Yale University Press, pp.83-85