In practice, therefore, if not in theory, the tendency of evolution has been to unspiritualize and dereligionize the philosophy of its adherents, a tendency which is strikingly exemplified in one of its greatest exponents, Charles Darwin himself. The English naturalist began his scientific career as a theist and a spiritualist. He ended it as an agnostic and a materialist. His evolutionary philosophy was, by his own confession, responsible for the transformation. “When thus reflecting,” he says, “I feel compelled to look to a first cause having an intelligent mind in some degree analogous to that of man, and I deserve to be called a Theist. This conclusion was strong in my mind about the time, as far as I remember, when I wrote the ‘Origin of Species’; and it is since that time that it has very gradually, with many fluctuations, become weaker. But then arises the doubt, can the mind of man, which has, as I fully believe, been developed from a mind as low as that possessed by the lowest animals, be trusted when it draws such grand conclusions? I can not pretend to throw the least light on such abstruse problems. The mystery of the beginning of all things is insoluble by us; and I, for one, must be content to remain an Agnostic.” (“The Life and Letters of Charles Darwin,” edited by Francis Darwin, 1887, vol. I, p. 282.) Darwin likewise exemplifies in his own person the destructive influence exercised upon the æsthetic sense by exclusive adherence to the monistic viewpoint. Having alluded in his autobiography to his former predilection for poetry, music, and the beauties of nature, he continues as follows: “But now for many years I cannot endure to read a line of poetry: I have tried lately to read Shakespeare, and found that it nauseated me. I have also lost my taste for pictures and music.... I retain some taste for fine scenery, but it does not cause me the exquisite delight which it formerly did.... My mind seems to have become a kind of machine for grinding general laws out of large collections of facts; ... if I had to live my life again, I would have made it a rule to read some poetry and listen to some music at least every week; for perhaps the parts of my brain now atrophied would have been kept alive through use. The loss of these tastes is a loss of happiness, and may possibly be injurious to the intellect, and more probably to the moral character by enfeebling the emotional part of our nature.” (_Op. cit._, vol. I, pp. 81, 82.)