"Nothing is so difficult to understand as that of which one is ignorant, nothing more simple than what one knows. Who is surprised now to see that the electric telegraph instantly sends human thought across continents and seas? Who is surprised to see lunar attraction raise the waters of the ocean and produce tides? Who is surprised to see light transmit itself from one star to another at the rate of three hundred thousand kilometres per second? Besides, thinkers alone could appreciate the grandeur of these marvels; the vulgar are surprised at nothing. If some new discovery to-morrow should enable us to make signals to the inhabitants of Mars and receive replies from them, three quarters of mankind would think nothing of it the day after. Yes, the animating forces can transport themselves from one world to the other; not everywhere nor always, to be sure, and not all of them. There are laws and conditions. My will, with the help of my muscles, can raise my arm or throw a stone; if I take a weight of twenty kilos, it will still raise my arm; if I want to raise a weight of a thousand kilos, I can no longer do it. Some minds are incapable of any activity; others have acquired transcendent faculties. Mozart at six years of age surprised all his hearers by the power of his musical genius, and at eight published his first two sonatas; while the greatest dramatic author who ever existed, Shakspeare, had written nothing worthy of his name until after he was thirty years old. It is not necessary to believe that the soul should belong to some supernatural world. Everything is in Nature. It is hardly more than a hundred thousand years since terrestrial humanity evolved itself from the animal chrysalis. For millions of years, during the long historic series of the primary, secondary, and tertiary periods, there was not a single eye on the earth to see these grand sights, a single human mind to contemplate them. Progress has slowly raised the inferior souls of plants and animals; man is quite recent on the planet. Nature is in ceaseless progress, the universe is a perpetual growth, ascent is the supreme law.