Why should we trouble our heads with philosophical study? Why is it not enough to practice goodwill towards men? The answer to the second question is that the feeling of goodwill may vanish at the first bitter experience of being injured by other men. It will not suffice to depend on feeling alone; one must also get thoroughly and rationally convinced that goodwill is necessary under all circumstances, and not only for the benefit of others, but even for our own.
-- Notebooks Category 20: What Is Philosophy? > Chapter 1: Toward Defining Philosophy > # 161