It is an extraordinary fact that man in himself, so far as he avails himself of his sound mind, is the greatest and most precise physical apparatus that can be. And it is in fact the greatest evil of the newer physics that experiments are, as it were, separated from man himself, so that nature is recognised only in what is ascertained by artificial instruments. It is exactly so with calculation. Much is true which cannot be computed, just as much can never be experimentally demonstrated. Man, however, stands so high that that which otherwise admits of no representation is ...