What is the nature of man? Is the basic nature of man good or evil, or something else? What is the view of the Backroom's great minds on this matter?

I haven't seen a thread on good old philosophy around here for a while during my Backroom-lurking (except for the Flying Spaghetti Monster Club), and having a debate over the matter in debating class (having picked the easy subject with my friend ), so I thought to get a thread of it in here.