As to methods, there may be a million and then some, but principles are few. The man who grasps principles can successfully select his own methods.

Let us draw a lesson from nature, which always works by short ways. When the fruit is ripe, it falls.

Let us replace sentimentalism by realism and dare to uncover those simple and terrible laws which, be they seen or unseen, pervade and govern.

Few people know how to take a walk. The qualifications are endurance, plain clothes, old shoes, an eye for nature, good humor, vast curiosity, good speech, good silence and nothing too much.

Everything in Nature contains all the powers of Nature. Everything is made of one hidden stuff.

Science does not know its debt to imagination.

There is never a beginning, there is never an end, to the inexplicable continuity of this web of God, but always circular power returning into itself.