DEAR HENRY ADAMS,--I have been so "slim" since seeing you, and the baths here have so weakened my brain, that I have been unable to do any reading except trash, and have only just got round to finishing your "letter," which I had but half-read when I was with you at Paris. To tell the truth, it doesn't impress me at all, save by its wit and erudition; and I ask you whether an old man soon about to meet his Maker can hope to save himself from the consequences of his life by pointing to the wit and learning he has shown in treating a tragic subject. No, sir, you can't do it, can't impress God in that way. So far as our scientific conceptions go, it may be admitted that your Creator (and mine) started the universe with a certain amount of "energy" latent in it, and decreed that everything that should happen thereafter should be a result of parts of that energy falling to lower levels; raising other parts higher, to be sure, in so doing, but never in equivalent amount, owing to the constant radiation of unrecoverable warmth incidental to the process. It is customary for gentlemen to pretend to believe one another, and until some one hits upon a newer revolutionary concept (which may be tomorrow) all physicists must play the game by holding religiously to the above doctrine. It involves of course the ultimate cessation of all perceptible happening, and the end of human history. With this general conception as _surrounding_ everything you say in your "letter," no one can find any fault--in the present stage of scientific conventions and fashions. But I protest against your interpretation of some of the specifications of the great statistical drift downwards of the original high-level energy. If, instead of criticizing what you seem to me to say, I express my own interpretation dogmatically, and leave you to make the comparison, it will doubtless conduce to brevity and economize recrimination. To begin with, the _amount_ of cosmic energy it costs to buy a certain distribution of fact which humanly we regard as precious, seems to me to be an altogether secondary matter as regards the question of history and progress. Certain arrangements of matter _on the same energy-level_ are, from the point of view of man's appreciation, superior, while others are inferior. Physically a dinosaur's brain may show as much intensity of energy-exchange as a man's, but it can do infinitely fewer things, because as a force of detent it can only unlock the dinosaur's muscles, while the man's brain, by unlocking far feebler muscles, indirectly can by their means issue proclamations, write books, describe Chartres Cathedral, etc., and guide the energies of the shrinking sun into channels which never would have been entered otherwise--in short, _make_ history. Therefore the man's brain and muscles are, from the point of view of the historian, the more important place of energy-exchange, small as this may be when measured in absolute physical units.