What is often missed in these discussions, it seems to me, is that almost everything that happens with your character at the table is emergent - it develops through play. This includes equipment, level, hit points, and all the other mundane system-related variables, of course. But it also applies to the 'personality' of the character too, in my experience. Generally, they begin life as ciphers - not quite blank slates, as you may have some vague ideas about the type of character they are - but almost.
Personality comes with interaction with the game world, the other PCs, and with NPCs. Characters get fleshed out by their life experience, in other words. As usual, the 2nd edition DMG has it right (albeit stated in the context of giving advice on what level new PCs should be introduced to a campaign):
If at all possible, start characters at 1st level. The lowest character levels are like the early years of childhood. What happens to a character during these first adventures will do much to determine how that character will be role-played. Did Rath the Dwarf save the day by fool-hardily charging into battle when he was a mere 1st level? If he did, the odds are good the player will try it again and will begin to play Rath as a bold and reckless fellow.
On the other hand, if Rath was clobbered the first few times he rushed in, the player would begin to play Rath as a cautious, prudent fellow. Even the smallest events can have a great effect on low-level characters, so these events sharply etch the behavior of the character. Deny the player these beginning levels and you are stripping him of the opportunity to develop his character's personality.
It is through experience that PCs become fleshed out into real 'people', in other words, and starting off a new PC is like putting on a new pair of shoes. It takes a while to wear them in. This also means that players don't have full control over how their PC develops: the process is a pseudo-mystical mixture of design and the quasi-random emergent processes of interaction and events, with the primary emphasis on the emergent processes. This fact should be obvious to anybody who plays role playing games, I would suggest.