"It is plain that there is no separate essence called courage, no cup or cell in the brain, no vessel in the heart containing drops or atoms that make or give this virtue; but it is the right or healthy state of every man, when he is free to do that which is constitutional to him to do."

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The story is told of Lord Kelvin, a famous Scotch physicist of the last century, that after he had given a lecture on atoms and molecules, one of his students came to him with the question, "Professor, what is your idea of the structure of the atom." "What," said Kelvin, "The structure of the atom? Why, don't you know, the very word 'atom' means the thing that can't be cut. How then can it have a structure?" "That," remarked the facetious young man, "shows the disadvantage of knowing Greek."

— Arthur Compton