Whole Sort Of Genl Mish Mash
I think Socrates/Plato might have been agnostic as to the Greek pantheon of gods as it was presented in his day, but Plato's Dialogues seem to show he did believe in a God or gods who could be reached through the practice of good philosophy.
A good source for Socrates'/Plato's thoughts on the soul can be found in Phaedo (not to be confused with Phaedrus, which is a Dialogue on love and rhetoric - I'll use "Plato" for the rest of my reply per Brad's correct point). If you get a good translation, it is a pretty easy read. Really interesting stuff, in my opinion.
To your post, I believe Plato's view's most resemble Brad's #3, but I'm not so sure Aristotle's didn't have some attribute's of #3 and #5. Brad, perhaps you wouldn't be confused by the apparent need to cultivate something that is already perfect if you understood Plato's views on the compound nature of the body and soul. Plato taught that the body and soul are a compound of the corporeal and incorporeal, the dissoluble and indissoluble. When the body dies, it decays and the soul remains after the compound is broken, but is not necessarily completely freed from the body's influence. His views on reincarnation, I think, illustrate how he saw our Earthly baggage as dead-weight that prevents the soul from having the requisite purity to ascend to the gods. When the body dies, and the soul does not ascend to the gods, it returns to Earth in forms consistent with that soul's human nature. The only way to escape this cycle, according to Plato, was through reason ... only philosophers ("lovers of knowledge") who attain a pure state (freedom from the controlling influences of pleasure and fear) can reach the gods.
I think you would probably find plenty of agnostics that are willing to accept the possibility that there is something of us ... our essence or something of our person ... that survives death (Brad & rwood, this is the definition I prefer). A true agnostic will either tell you that he/she doesn't know for sure that the soul exists or that you cannot know for certain that the soul exists.
Ask a theist and you might receive 20 different answers (isn't that right, Stephen?).
As for me ... I think that souls probably exist and the fact they exist is probably important, but what the soul is comprised of and the attributes souls possess are more matters of curiosity than of any immediate practical importance.
rwood, many thanks for posting a thread the brings the classics into the discussion.