The Riddle of the Universe

Ernst Haeckel had spent forty years as a working zoologist before he turned, at the close of the nineteenth century, to the questions he believed biology had finally settled. His argument is monism: mind and matter, God and nature, are not two things but one, and the soul is a function of the body rather than a guest inside it. He works through the origin of life, the descent of humans, consciousness, immortality and the claims of the churches, treating each as a scientific problem rather than a mystery. The book sold in enormous numbers across Europe and drew furious replies from theologians and uneasy ones from scientists, which was more or less what Haeckel wanted. Free PDF and EPUB editions are available here.