A gem cannot be polished without friction, nor a man perfected without trials.
A pure hand needs no glove to cover it.
Whoever undertakes to set himself up as a judge of Truth and Knowledge is shipwrecked by the laughter of the gods.
It is not enough to have a good mind; the main thing is to use it well.
It isn't the mountain ahead that wears you out; it's the grain of sand in your shoe.
One of the greatest joys known to man is to take a flight into ignorance in search of knowledge.
The farther reason looks the greater is the haze in which it loses itself.
Yesterday's home runs don't win today's games.
In the end, people are persuaded not by what we say, but by what they understand.
The very essence of instinct is that it's followed independently of reason.
Important principles may, and must, be inflexible.
We are all gifted. That is our inheritance.
One can resist the invasion of an army but one cannot resist the invasion of ideas.
A certain amount of opposition is a great help to a man. Kites rise against, not with, the wind.
Lend yourself to others, but give yourself to yourself.
The soul is placed in the body like a rough diamond, and must be polished, or the luster of it will never appear.
A man must not deny his manifest abilities, for that is to evade his obligations.
Every man must decide for himself whether he shall master his world or be mastered by it.
Never mistake motion for action.
The precision of naming takes away from the uniqueness of seeing.