We all try to escape pain and death, while we seek what is pleasant.

But nature did not deem it her business to make the discovery of her laws easy for us.

All our thoughts and concepts are called up by sense-experiences and have a meaning only in reference to these sense-experiences. On the other hand, however, they are products of the spontaneous activity of our minds; they are thus in no wise logical consequences of the contents of these sense-experiences. If, therefore, we wish to grasp the essence of a complex of abstract notions we must for the one part investigate the mutual relationships between the concepts and the assertions made about them; for the other, we must investigate how they are related to the experiences.

Something deeply hidden had to be behind things.

People should be more like animals . . . they should be more intuitive; they should not be too conscious of what they do while they do it.

A man's value to the community primarily depends on how far his feelings, thoughts, and actions are directed towards promoting the good of his fellows.

For scientific endeavor is a natural whole the parts of which mutually support one another in a way which, to be sure, no one can anticipate.