This is the first volume of the 1959-1960 Gifford Lectures, delivered by one of the foremost physicists and cosmologists of our time. The author makes a comprehensive survey of cosmological myths, from ancient times down to the era when scientific theories and explanations began to displace mythological interpretations as a way of understanding and interpreting the cosmos. The final chapter gives an exceedingly pregnant discussion of Secularism as the dominant mode of life and thought today, and one that calls for a thorough-going revision of much traditional Christian thinking. Secularization is itself a consequence of the new energies and attitudes released by the Gospel. Because the Church has not been aware of the powerful transformations wrought by the Gospel, it now finds itself following, rather than leading, the historical process. Great learning is joined here with deep personal Christian commitment and a stirring vision of the future.