 The book proposed a version of orthogenesis in place of Darwin's mechanism of evolution, suggesting that evolution is motivated by the élan vital, a "vital impetus" that can also be understood as humanity's natural creative impulse.The book was very popular in the early decades of the twentieth century.The book also developed concepts of time (offered in Bergson's earlier work) which significantly influenced modernist writers and thinkers such as Marcel Proust and Thomas Mann.