Aṅguttara Nikāya
The Book of the Threes
3. Thinking
“Bhikkhus, the fool has these three characteristics of a fool, marks of a fool, manifestations of a fool. What three? Here, a fool thinks badly, speaks badly, and acts badly. If the fool did not think badly, speak badly, and act badly, how would wise people know of him: ‘This fellow is a fool, a bad person’? But because the fool thinks badly, speaks badly, and acts badly, wise people know of him: ‘This fellow is a fool, a bad person.’ These are the fool’s three characteristics of a fool, marks of a fool, manifestations of a fool.
“The wise person has these three characteristics of a wise person, marks of a wise person, manifestations of a wise person. What three? Here, a wise person thinks well, speaks well, and acts well. If the wise person did not think well, speak well, and act well, how would wise people know of him: ‘This fellow is wise, a good person’? But because the wise person thinks well, speaks well, and acts well, wise people know of him: ‘This fellow is wise, a good person.’ These are the wise person’s three characteristics of a wise person, marks of a wise person, manifestations of a wise person.
“Therefore … as in 3:2 … It is in this way that you should train yourselves.”