The nineteenth-century British naturalist Alfred Russel Wallace was a major influence on Darwin's theory of natural selection. He was later moved by a variety of personal experiences to examine the concept of spirituality, but his exploration into the potential for compatibility between spiritualism and natural selection alienated him from the scientific community. The three controversial essays in this 1875 book attempt to reinforce his beliefs and validate his claims. The first, written in 1871 and read before The Dialectic Society, reconsiders the credibility or incredibility of miracles. The second, 'The Scientific Aspect of the Supernatural', had been published in a secularist periodical several years earlier, and 'A Defence of Modern Spiritualism' appeared in the Fortnightly Review shortly before this book was published. Wallace's book takes the modern reader to the heart of the raging debates engendered by Darwin, many of which continue over a century later.