The infinite wealth of nature in what is beautiful and sublime offers every man with open eyes and an æsthetic sense an incalculable sum of choicest gifts. Still, however valuable and agreeable is the immediate enjoyment of each single gift, its worth is doubled by a knowledge of its meaning and its connection with the rest of nature. When Humboldt gave us the "outline of a physical description of the world" in his magnificent _Cosmos_ forty years ago, and when he combined scientific and æsthetic consideration so happily in his standard _Prospects of Nature_, he justly indicated how closely the higher enjoyment of nature is connected with the "scientific establishment of cosmic laws," and that the conjunction of the two serves to raise human nature to a higher stage of perfection. The astonishment with which we gaze upon the starry heavens and the microscopic life in a drop of water, the awe with which we trace the marvellous working of energy in the motion of matter, the reverence with which we grasp the universal dominance of the law of substance throughout the universe--all these are part of our emotional life, falling under the heading of "natural religion." This progress of modern times in knowledge of the true and enjoyment of the beautiful expresses, on the one hand, a valuable element of our monistic religion, but is, on the other hand, in fatal opposition to Christianity. For the human mind is thus made to live on this side of the grave; Christianity would have it ever gaze beyond. Monism teaches that we are perishable children of the earth, who for one or two, or, at the most, three generations, have the good fortune to enjoy the treasures of our planet, to drink of the inexhaustible fountain of its beauty, and to trace out the marvellous play of its forces. Christianity would teach us that the earth is "a vale of tears," in which we have but a brief period to chasten and torment ourselves in order to merit the life of eternal bliss beyond. Where this "beyond" is, and of what joys the glory of this eternal life is compacted, no revelation has ever told us. As long as "heaven" was thought to be the blue vault that hovers over the disk of our planet, and is illumined by the twinkling light of a few thousand stars, the human imagination could picture to itself the ambrosial banquets of the Olympic gods above or the laden tables of the happy dwellers in Valhalla. But now all these deities and the immortal souls that sat at their tables are "houseless and homeless," as David Strauss has so ably described; for we know from astrophysical science that the immeasurable depths of space are filled with a prosaic ether, and that millions of heavenly bodies, ruled by eternal laws of iron, rush hither and thither in the great ocean, in their eternal rhythm of life and death.