Possible Clues:

• Philosopher unconventional to realist
• A great thinker, tries a lot to be different
• Originator of the maxim 'One swallow does not make a summer'
• 'Metaphysica' writer
• Realist unsettled, but holding to philosopher
• Great Greek philosopher, pupil of Plato
• A knight rising to let out Alexander's mentor
• Great Greek philosopher of 4th century B.C.
• Peripatetic teacher from Plato's Academy
• Realist to upset philosopher