Kuczynski: Philosophy is thinking about thinking.
William James: Philosophy is an unusually obstinate attempt to think clearly.
Kant: Philosophy studies that categories whose logical integrity empirical science assumes.
Freud: Philosophy mimics science and up to a point operates according to its methods, but involves an overestimation of the epistemic value of our logical operations.
Aquinas: Philosophy is religion rationalized.
Nietzsche: Philosophy is how impotent nerds get revenge on potent warriors.
Kuczynski (again): Philosophy is intellectualized withdrawal.