In the Preface to Civilization and Ethics (1923) he argued that Western philosophy from Descartes to Kant had set out to explain the objective world expecting that humanity would be found to have a special meaning within it. But no such meaning was found, and the rational, life-affirming optimism of the Age of Enlightenment began to evaporate. A rift opened between this world-view, as material knowledge, and the life-view, understood as Will, expressed in the pessimist philosophies from Schopenhauer onward. Scientific materialism (advanced by Herbert Spencer and Charles Darwin) portrayed an objective world process devoid of ethics, entirely an expression of the will-to-live.