Though, arguably, if one is a true Platonist, one should view roles as Aristotelian, and base classes as Platonic and therefore more "real"...but I'm more of an Aristotelian myself, so I tend to think of the Platonic ideals as less real than reality.
Whatever. Both Plato and Aristotle would probably have hated our modern conceptions of what they thought. But I suspect Plato would have liked Smalltalk or ML, while Aristotle would doubtless be programming in something like Self, or maybe C... Larry