"The parasites which live in the intestines of higher animals, feeding upon the nutritive juices which these animals supply, do not need either to see or hear, and therefore for them the visible and audible world does not exist. And if they possessed a certain degree of consciousness and took account of the fact that the animal at whose expense they live believed in a world of sight and hearing, they would perhaps deem such belief to be due merely to the extravagance of its imagination. And similarly there are social parasites, as Mr. A. J. Balfour admirably observes, who, receiving from the society in which they live the motives of their moral conduct, deny that belief in God and the other life is a necessary foundation for good conduct and for a tolerable life, society having prepared for them the spiritual nutriment by which they live. An isolated individual can endure life and live it well and even heroically without in any sort believing either in the immortality of the soul or in God, but he lives the life of a spiritual parasite."