Defining an adult - question

[marita_c]

This is for something that I’m writing:

Let’s say that a man (21+ y.o.) has ‘amnesia’: His language capabilities are intact, he can still win a game of Trivia, can operate a computer and play the piano – BUT his episodic memory is gone for good. He doesn’t know who he is, has absolutely no recollection of any previous experiences, events or people. 100% clean slate.

Many people say that it’s the experience the shapes the person – what you’ve been through throughout your life has made you into what you are.

According to this, once that man suffers said amnesia, he’s reduced, in many ways, to an infant. Would you consider that person to be an adult? Would you allow him to vote, drink alcohol, have sex?