the wise man questions one's self, the fool questions…
Page 67 the wise man questions one's self, the fool questions others.
— from Who Is Flying (Self, Nature & Nurture)
In the book
Now the pilot — and knowing him is the labor of a lifetime. Sun Tzu's ancient counsel still holds: know yourself, and you need not fear a hundred battles; the wise man questions himself, while the fool questions everyone else. The first rule is simply to learn how to know yourself — to identify your own mind, your strengths and weaknesses, your real motives — because only once you see how you actually regard yourself can you begin to find your true self. — Who Is Flying (Self, Nature & Nurture)