LUMEN. We have no right to declare an unknown fact impossible, when we are so ignorant ourselves of the laws regulating our own being. Because the brain is the physiological organ of intelligence placed at the service of man on the Earth, do you therefore believe that there are similar brains and spinal marrows upon all the worlds in space? This would be an error too childish. The law of progress governs the vital system of each world. This vital system differs according to the secret nature of the special forces peculiar to each. When a world has reached a sufficient degree of evolution to fit it for entering into the service of moral life, _mind_, more or less developed, appears on it. [Sidenote: Gradation of the human race.] Do not imagine that the Eternal Father creates at once a human race on each globe. Not so. The first step in the ladder of the animal kingdom receives the human transfiguration by force of circumstance, and by natural law, which ennobles it, as soon as progress has brought it to a state of relative superiority. [Sidenote: The development of life.] Do you know why you have a chest, a stomach, two legs, two arms, and a head furnished with visual, auditory, and olfactory senses? It is because the quadrupeds, the mammalia, which preceded the appearance of man on the Earth, had them already. Monkeys, dogs, lions, bears, horses, oxen, tigers, cats, &c., and before them the horned rhinoceros, the cave-hyena, the elk, the mastodon, the oppossum, &c., and prior to these the pleiosaurus, the ichthyosaurus, the iguanodon, the pterodactyl, &c., and again before these the fishes, the crustacea, the mollusca, &c., have been the result of the vital forces in action upon the Earth, dependent upon the state of the soil, of the atmosphere, of inorganic chemistry, of the quantity of heat, and of terrestrial gravity. The earthly animal kingdom has followed, from its origin, this continuous and progressive march towards the perfection of its typical forms of mammalia, freeing itself more and more, from the grossness of its material. Man is more beautiful than the horse, the horse than the bear, the bear than the tortoise. A similar law governs the vegetable kingdom. Heavy, coarse vegetables without leaves and without flowers began the series. Then, as the ages advanced, their forms became more pure, and graceful leaves appeared filling the woods with silent shadows. Flowers in their turn began to beautify the gardens of the Earth, and spread sweet perfumes in an atmosphere until then insipid. [Sidenote: The genealogical tree of life.]