Uncompromising thought is the luxury of the closeted recluse. Untrammeled reasoning is the indulgence of the philosopher, of the dreamer of sweet dreams.

A man's thinking goes on within his consciousness in a seclusion in comparison with which any physical seclusion is an exhibition to public view.

Things thought too long can be no longer thought, For beauty dies of beauty, worth of worth, And ancient lineaments are blotted out.

To be free from evil thoughts is God's greatest gift.

Your thoughts are a machine you can learn to operate.

It is a joy to be choked with thought.

The manner in which one single ray of light, one single precious hint, will clarify and energize the whole mental life of him who receives it, is among the most wonderful and heavenly of intellectual phenomena.

I think that I think, therefore I think that I am.

The busiest of living agents are certain dead men's thoughts.

First doubt, then inquire, then discover. This has been the process with all our great thinkers.