Plato

[andrews]

Plato's primary philosophical concern was?

[WoWo]

The nature of homework

[bernardo]

The impenetrability of matter, or the ungetthroughableness of stuff

[el duerino]

http://classics.mit.edu/Browse/browse-Plato.html ;)

[NoGood Boyo]

Looking after Mickey Mouse and Donuld Dack.

[Brugel]

Probably to discover the truth about various things like courage, justice and beauty by the method of Socratic enquiry. But your question is too vague- you'll have to supply more background detail to it.