Possible Clues:

• Philosopher's books mount up
• Greek philosopher; crater on the moon
• Athenian philosopher, pupil of Socrates
• One turning up among pivotal philosophers
• First philosopher to mention Atlantis
• Source of many dialogues
• Philosopher's note in instruction at bottom of page?
• Philosopher who said 'Writing is the geometry of the soul'
• Philosopher who gets on with soldiers
• "Theory of Forms" philosopher