People are always talking about originality; but what do they mean? As soon as we are born, the world begins to work upon us; and this goes on to the end. And after all, what can we call our own, except energy, strength, and will? If I could give an account of all that I owe to great predecessors and contemporaries, there would be but a small balance in my favor.

There is no permanence in doubt; it incites the mind to closer inquiry and experiment, from which, if rightly managed, certainty proceeds, and in this alone can man find thorough satisfaction.

So, lively brisk old fellow, don't let age get you down. White hairs or not, you can still be a lover.

No two men see the world exactly alike, and different temperaments will apply in different ways a principle that they both acknowledge.

Someday someone will write a pathology of experimental physics and bring to light all those swindles which subvert our reason, beguile our judgement and, what is worse, stand in the way of any practical progress. The phenomena must be freed once and for all from their grim torture chamber of empiricism, mechanism, and dogmatism; they must be brought before the jury of man's common sense.

The sum which two married people owe to one another defies calculation. It is an infinite debt, which can only be discharged through all eternity.

I hate everything that merely instructs me without augmenting or directly invigorating my activity.