But it is childish to talk of happiness and unhappiness where infinity is in question. The idea which we entertain of happiness and unhappiness is something so special, so human, so fragile that it does not exceed our stature and falls to dust as soon as we take it out of its little sphere. It proceeds entirely from a few contingencies of our nerves, which are made to appreciate very slight happenings, but which could as easily have felt everything the opposite way and taken pleasure in that which is now pain. I do not know if my readers remember the striking passage in which Sir William Crookes shows how well-nigh all that we consider as essential laws of nature would be falsified in the eyes of a microscopic man, while forces of which we are almost wholly ignorant, such as surface-tension, capillarity, the Brownian movements, would preponderate. Walking on a cabbage-leaf, for instance, after the dew had fallen, and seeing it studded with huge crystal globes, he would infer that water was a solid body which assumes spherical form and rises in the air. At no great distance, he might come to a pond, when he would observe that this same matter, instead of rising upwards, now seems to slope downwards in a vast curve from the brink. If he managed, with the aid of his friends, to throw into the water one of those enormous steel bars which we call needles, he would see that it made a sort of concave trough on the surface and floated tranquilly. From these experiments and a thousand others which he might make, he would naturally deduce theories diametrically opposed to those upon which our entire existence is based. It would be the same if the changes were made in the direction of time, to take an hypothesis imagined by the philosopher William James: