As for everything else, so for mathematical theory: beauty can be perceived but not explained.
To state a theorem and then to show examples is literally to teach backwards.
It is mathematics that offers the exact natural sciences a certain measure of security which, without mathematics, they could not attain.
If a person commit a crime against you, have not the right to forgive him; but the law must punish him in order to prevent a repetition of that same crime by others, as the pain of the individual is unimportant beside the general welfare of the people.
The most important principle of divine philosophy is the oneness of the world of humanity, the unity of mankind, the bond conjoining East and West, the tie of love which blends human hearts.
If a man has ten good qualities and one bad one, to look at the ten and forget the one, and if a man has ten bad qualities and one good one, to look at the one and forget the ten.
Do not be content with showing friendship in words alone, let your heart burn with loving kindness for all who may cross your path.
I never saw a wild thing sorry for itself. A bird will fall frozen dead from the bow of a ship without ever having felt sorry for itself.