This book presents an introduction to the metaphysical philosophy of nature put forward by Hedwig Conrad-Martius (1888-1966). Providing a unique perspective on central issues in modern and contemporary theoretical biology and physics, it will be of interest to anyone studying the history of the phenomenological movement as well as religious cosmology. The philosophical basis for this cosmology is Conrad-Martius' "realontology"-a phenomenological account of the essence of reality. His position centers on the revival of ancient metaphysical themes in new transformed guises, especially potentiality and entelechy. Nature's status, as a self-actuation of world-constituting essence-entelechies, places Conrad-Martius at the heart of philosophical-theological discussions of e.g. the hermeneutical mandate of demythologization as well as the nature of evolution. Of special interest is his insistence on both nature's self-actuating and evolving powers and a robust theory of creation. .