In his works, Tennyson combined his interest for science with his (unorthodox) Christian faith. Tennyson was particularly interested in geology and biology. He was influenced by the elaboration of the theory of evolution which is usually credited to Darwin's Origin of the Species in 1859. Yet, the development of the theory of evolution had been taking form for several decades and, in In Memoriam (written between the 1830s and 1850). Tennyson anticipated several key ideas of Darwin's theory. The poet probably drew from Charles Lyell's Principles of Geology (1830-33). In the lyric 56 of In Memoriam Tennyson explicitly writes of his difficulty to reconcile his faith in God with the new scientific theory of evolution. The laws of Nature "shriek'd against his creed". The lyrics in the poem thus dramatize the conflict between the scientific discoveries of the Victorian Age and man's necessity to hold on to his religious faith. Yet, Tennyson was able to read the changes and progress of his era, not as a chaotic but as an ordered and planned movement that tended to man's final union with God. Tellingly, in Idylls of the King, Tennyson wrote that that "the old order changeth, yielding place to new/ And God fulfils Himself in many ways". The lines express the poet's belief that the changes that he is witnessing are orchestrated by God's superior intelligence.