(Note: This interview first aired last fall.) How long has atheism been a part of human experience? Most people today regard the sustained, intellectually rigorous adherence to non-religion as an invention of the European Enlightenment -- or, more recently, of modernity. But as our guest argues on this edition of ST, atheism is actually -- like so many other aspects of Western life and culture -- a phenomenon with origins in the societies of the ancient Mediterranean. Our guest is Tim Whitmarsh, the Leventis Professor of Greek Culture at the University of Cambridge; he has published widely on ancient Greek and Roman texts, and he chats with us about his fascinating new book, "Battling the Gods: Atheism in the Ancient World." Myths, legends, rituals, dramas, and epic poems concerning the gods obviously mattered greatly in -- and were fundamental to -- ancient Greece and Rome alike, but Whitmarsh has several interesting points to make about the various writers and thinkers who challenged if not dismissed these very gods' existence. For example: Diagoras of Melos, perhaps the first-ever self-professed atheist; Democritus, the first materialist; Lucretius, author of "On the Nature of Things," a crucial work of proto-scientific writing; and Socrates, who was famously executed for rejecting the gods of (and thereby corrupting the youth of) the Athenian state. As was noted of Whitmarsh's book in a starred review in Kirkus: "A seminal work...to be studied, reread, and referenced.... With a non-professorial, relaxed style...Whitmarsh delves deeply into the many philosophers who felt gods were invented by humans or who saw laws, in addition to religion, as merely the imposition of order.... The author's erudition is impressive." You can learn more about this book, and can hear a free, on-demand stream of our discussion with its author, at this link.