Knowledge is true opinion.

Opinion is the medium between knowledge and ignorance.

Either we shall find what it is we are seeking or at least we shall free ourselves from the persuasion that we know what we do not know.

To appreciate the beauty of a snow flake, it is necessary to stand out in the cold.

Not one of them who took up in his youth with this opinion that there are no gods, ever continued until old age faithful to his conviction.

Knowledge is the food of the soul.