Memory and Personal Identity

Come join us for some informal philosophical discussion. No prior knowledge or research is required, but an open mind is.
What makes you the same person over time? Perhaps you feel like an entirely different person from who you were ten years ago: your tastes changed, your beliefs changed, your body changed, your memories faded, and perhaps you now look back on your former self with embarrassment. And yet other people (and the government) treat you as one continuous person from birth to death. Your debts, achievements, crimes, promises, and driver’s license all seem to belong to the same "you". The most obvious source of personal identity is memory. Memory gives us continuity from day to day: most of us feel pretty confident that we are the same person we were five minutes ago. But memory is an unreliable foundation.

• Neurologist Oliver Sacks once described a patient who committed murder while high on drugs and then lost all memory of the crime. Since he could feel no guilt for an act he could not remember, Sacks wondered whether it was even fair to punish him as the same person. Years later, the memories returned, burdening the man with heavy guilt.
• Philosopher Derek Parfit challenged the very idea that personal identity is what matters. In his famous teletransporter thought experiment, a machine scans your body and mind, destroys you on Earth, and recreates an exact copy on Mars. Did you survive? What if the original is not destroyed, and now there are two "yous"?
• Psychologist Daniel Kahneman added another twist by distinguishing the "experiencing self" and the "remembering self", whose interests often differ greatly. For example, would you choose a wonderful vacation if afterward all memories and photos of it were erased? This would gratify your experiencing self while leaving the remembering self empty-handed.

Further questions:

• Were you ever really the infant whose baby photos your parents show you?
• If your memories were gradually replaced with someone else's memories, at what point would you stop being you?
• If your personality changed completely after a brain injury, would your friends and family owe loyalty to the "new you" in the same way?
• Should people be forgiven more easily for things they did when they were "a different person"?
• If uploading your mind to a computer became possible, would that be survival, replacement, or just a very flattering memorial?
• If you discovered that many of your cherished memories were false, would you feel that your identity had been damaged?