If [science] tends to thicken the crust of ice on which, as it were, we are skating, it is all right. If it tries to find, or professes to have found, the solid ground at the bottom of the water it is all wrong. Our business is with the thickening of this crust by extending our knowledge downward from above, as ice gets thicker while the frost lasts; we should not try to freeze upwards from the bottom.