Spiritual power is a force which history clearly teaches has been the greatest force in the development of men. Ye. we have been merely playing with it and never have really studied it as we have the physical forces. Some day people will learn that material things do not bring happiness, and are of little use in making people creative and powerful. Then the scientists of the world will turn their laboratories over to the study of spiritual forces which have hardly been scratched.

Take the rose—most people think it very beautiful: I don’t care for It at all. I prefer the cactus, for the simple reason that it has a more interesting personality. It has wonderfully adapted itself to its surroundings! It is the best illustration of the theory of evolution in plant life.

The most important advance in the next fifty years will be in the realm of the spiritual - dealing with the spirit of thought.

Indeed, the most important part of engineering work-and also of other scientific work-is the determination of the method of attacking the problem, whatever it may be, whether an experimental investigation, or a theoretical calculation. ... It is by the choice of a suitable method of attack, that intricate problems are reduced to simple phenomena, and then easily solved.

[I predict] the electricity generated by water power is the only thing that is going to keep future generations from freezing. Now we use coal whenever we produce electric power by steam engine, but there will be a time when there'll be no more coal to use. That time is not in the very distant future. ... Oil is too insignificant in its available supply to come into much consideration.

No man really becomes a fool until he stops asking questions.

As for my memory, I have a particularly good one. I never keep any record of my investigations or experiments. My memory files all these things away conveniently and reliably. I should say, though, that I didn’t cumber it up with a lot of useless matter.