Atheism has achieved renewed vigor in the West in recent years with a spate of bestselling books and growing membership in secularist and rationalist organizations. The publication of Richard Dawkins’ The God Delusion in 2006 was a major cultural event. It signaled the beginning of a phenomenon now commonly known as the ‘New Atheism’. This article sets the context for the emergence of the movement. The author recognizes two streams of thought, scientific atheism and humanistic atheism. The first closely associated with Darwinism and Enlightenment rationalism, the second aligned with the rise of the social sciences and pioneered by Marx and Feuerbach. The study presents historical analysis to contextualize and enrich understanding of the trends. It outlines the growing tension between the two distinct streams within the movement and considers how the relationship between the two should be a focus of future research.