When intelligent and sensible people despise knowledge in their old age, it is only because they have asked too much of it and of themselves.

If the world does improve on the whole, yet youth must always begin anew, and go through the stages of culture from the beginning.

Even though the world as a whole progresses, youth must always start again from the beginning, and as individuals go through the epochs of the world's culture.

Nine requisites for contented living: Health enough to make work a pleasure. Wealth enough to support your needs. Strength to battle with difficulties and overcome them. Grace enough to confess your sins and forsake them. Patience enough to toil until some good is accomplished. Charity enough to see some good in your neighbor. Love enough to move you to be useful and helpful to others. Faith enough to make real the things of God. Hope enough to remove all anxious fears concerning the future.

The highest problem of any art is to cause by appearance the illusion of a higher reality.

The greater the knowledge, the greater the doubt.

Without my attempts in natural science, I should never have learned to know mankind such as it is. In nothing else can we so closely approach pure contemplation and thought, so closely observe the errors of the senses and of the understanding, the weak and strong points of character.