This book examines the philosophies of nature of the early Greek thinkers and argues that a significant and thoroughgoing shift is required in our understanding of them. In contrast with the natural world of the earliest Greek literature, often the result of arbitrary divine causation, in the work of early Ionian philosophers we see the idea of a cosmos: ordered worlds where there is complete regularity. How was this order generated and maintained and what underpinned those regularities? What analogies or models were used for the order of the cosmos? What did they think about causation and explanatory structure? How did they frame natural laws? Andrew Gregory draws on recent work on mechanistic philosophy and its history, on the historiography of the relation of science to art, religion and magic, and on the fragments and doxography of the early Greek thinkers to argue that there has been a tendency to overestimate the extent to which these early Greek philosophies of nature can be described as ‘mechanistic’. We have underestimated how far they were committed to other modes of explanation and ontologies, and we have underestimated, underappreciated and indeed underexplored how plausible and good these philosophies would have been in context.