Charles Darwin's views on religion have been the subject of much interest and dispute. His pivotal work in the development of modern biology and evolution theory played a prominent part in debates about religion and science at the time. In the early 20th century, his contributions became a focus of the creation–evolution controversy in the United States. While Darwin came to heavily dispute the dogmatic prescriptions of the Anglican Church and Christianity in general, later in life he clarified his position as an agnostic in response to a letter from John Fordyce: "In my most extreme fluctuations I have never been an atheist in the sense of denying the existence of a God.— I think that generally (& more and more so as I grow older) but not always, that an agnostic would be the most correct description of my state of mind." Charles Darwin had a non-conformist Unitarian background, but attended an Anglican school. With the aim of becoming a clergyman, he went to the University of Cambridge for the required Bachelor of Arts degree, which included studies of Anglican theology. He took great interest in natural history and became filled with zeal for science as defined by John Herschel, based on the natural theology of William Paley which presented the argument from divine design in nature to explain adaptation as God acting through laws of nature. On the voyage of the Beagle he remained orthodox and looked for "centres of creation" to explain distribution, but towards the end of the voyage began to doubt that species were fixed. By this time he was critical of the Bible as history, and wondered why all religions should not be equally valid. Following his return in October 1836, he developed his novel ideas of geology while speculating about transmutation of species and thinking about religion. Following Darwin's marriage to Emma Wedgwood in January 1839, they shared discussions about Christianity for several years, Emma's views being Unitarian like much of her family. The theodicy of Paley and Thomas Malthus vindicated evils such as starvation as a result of a benevolent creator's laws which had an overall good effect. To Darwin, natural selection produced the good of adaptation but removed the need for design, and he could not see the work of an omnipotent deity in all the pain and suffering such as the ichneumon wasp paralysing caterpillars as live food for its