No man is so foolish but he may sometimes give another good counsel, and no man so wise that he may not easily err if he takes no other counsel than his own. He that is taught only by himself has a fool for a master.

He who is not master of his own thoughts is not accountable for his own deeds.

Only a fool learns from his own mistakes. The wise man learns from the mistakes of others.

He could teach his students nothing. He was only educating himself at their cost.

A person is a fool to become a writer. His only compensation is absolute freedom. He has no master except his own soul, and that, I am sure, is why he does it

If you are not willing to be a fool, you can't become a master.

Every person of learning is finally his own teacher; the reason of which is, that principles, being of a distinct quality to circumstances, cannot be impressed upon the memory; their place of mental residence is the understanding, and they are never so lasting as when they begin by conception.

The man who does not do his own thinking is a slave, and is a traitor to himself and to his fellowmen.

Whoever among you thinks himself wise must become a fool to be truly wise

He is a poor pupil who does not go beyond his master.

the wise may be instructed by a fool

The doctor who treats himself has a fool for a patient.

No teacher is greater than one’s own experience.

Do not believe that you alone can be right.
The man who thinks that,
The man who maintains that only he has the power
To reason correctly, the gift to speak, the soul — A man like that, when you know him, turns out empty.