The Philosopher as Rhinoceros

George Santayana, Character and Opinion in the United States (New York: Norton, 1967), p. 35:

So long as philosophy is the free pursuit of wisdom, it arises wherever men of character and penetration, each with his special experience or hobby, looks about them in this world. That philosophers should be professors is an accident, and almost an anomaly. Free reflection about everything is a habit to be imitated, but not a subject to expound; and an original system, if the philosopher has one, is something dark, perilous, untested, and not ripe to be taught, nor is there much danger that anyone will learn it. The genuine philosopher -- as Royce liked to say, quoting the Upanishads -- wanders alone like the rhinoceros.

Is it any wonder that Santayana quit his teaching job at Harvard and spent the rest of his life in retirement in Rome?

The difference between a philosopher and a professor of philosophy is the former lives for what the latter lives from.