Plato is my friend — Aristotle is my friend — but my greatest friend is truth.

This is a variation on a much older adage, which Roger Bacon attributed to Aristotle: Amicus Plato sed magis amica veritas. Bacon was perhaps paraphrasing a statement in the Nicomachean Ethics: Where both are friends, it is right to prefer truth.

s: Plato is my friend, Aristotle is my friend, but my best friend is truth. Plato is my friend — Aristotle is my friend — truth is a greater friend.