We can't solve today's problems with the mentality that created them.

Strange is our situation here on earth. Each of us comes for a short visit, not knowing why, yet sometimes seeming to divine a purpose.

It is humankind's duty to respect all life, not only animals have feelings but even also trees and plants.

Insofar as we may at all claim that slavery has been abolished today, we owe its abolition to the practical consequences of science

Nothing happens unless something moves.

Make everything as simple as possible, but not simpler.

I soon learned to scent out that which was able to lead to fundamentals and to turn aside from everything else, from the multitude of things which clutter up the mind and divert it from the essential.