The calculation of probabilities supplies an answer to this question. The greater the number of worlds, the greater will be the probability that the forces of nature have given birth to an organisation like that of the Earth. Now the real number of worlds surpasses all human calculation, either written or possible to be written. If we could understand what "infinite" means, we might venture to say that this number is infinite. I concluded, then, that there is a very high probability in favour of the existence of many worlds exactly like the Earth, on the surface of which the same history is accomplished, and the same succession of historical events takes place; worlds which are inhabited by identically the same species of vegetables and animals, and the same humanity, and where men and families like our own, I doubt not, exist. In the second place, I asked myself if another world analogous to the Earth might not also be symmetrical to it; and then I worked out the geometry of the problem, and the metaphysical theory of images. I arrived at the conclusion that it was _possible_ for the world in question to be like the Earth, but in an inverse form. When you look at yourself in a mirror, you notice that the ring on your right hand appears to be on the ring-finger of your left hand. This explains the symbol. If you wink your right eye, your reflection winks the left eye; when you advance your right arm, your image advances the left arm. It is not impossible that in the infinity of the stars a world exists exactly the converse of the terrestrial world. Undoubtedly in an _infinity_ of worlds the non-existence of a similar world, perhaps of millions of them, would be the real impossibility. Nature of necessity repeats herself, reproduces herself, but still under all forms plays the game of creation. I thought therefore that the world on which I saw those things was not the Earth, but a globe like the Earth, the history of which was precisely the opposite of yours. QUÆRENS. I myself have had the idea also that it might have been as you say. But was it not easy for you to make sure of it by ascertaining whether it was the Earth or another star that you had before your eyes, by examining its astronomical position? [Sidenote: The solution of the problem.]