It is not a necessity, for though we can count on it happening practically, we have no right to say that it must always happen. We risk the remote possibility of a miracle as we do that of a poisoned pancake or a world-destroying comet. We leave it out of account, not because it is a miracle, and therefore an impossibility, but because it is a miracle, and therefore an exception. They express the arbitrariness of the fact and its mystery. A tree grows fruit because it is a magic tree.
Water runs downhill because it is bewitched.
The sun shines because it is bewitched. I deny altogether that this is fantastic or even mystical. Nay, the ordinary scientific man is strictly a sentimentalist. He is a sentimentalist in this essential sense, that he is soaked and swept away by mere associations. He has so often seen birds fly and lay eggs that he feels as if there must be some dreamy, tender connection between the two ideas, whereas there is none.