In this book Stephen Makin offers a striking new account of some intriguing but neglected arguments - indifference arguments - and of the presocratic atomism underpinned by indifference reasoning. Used by Parmenides, Democritus, Plato, Aristotle and Leibniz as well as some contemporary philosophers, indifference arguments start from claims about a balance of reasons or an absence of asymmetries. While some provide plausible support for surprisingly strong conclusions, others produce no conviction. Here, Makin offers an account of indifference arguments and provides answers to such philosophical questions as 'What makes a good piece of indifference reasoning?', 'How do the arguments work?', 'Do they involve claims about metaphysical commitments?' The account that is presented of the Democritean atomic theory strongly emphasizes the continuity of atomism with earlier thought. A number of Zeno's arguments are considered, and there is some discussion of other Eleatics. Indifference arguments in other ancient philosophers, such as Anaximander and Aristotle, also receive attention. The book will be of interest to all those concerned with ancient philosophy and philosophical logic.