Do you make your own choices or have circumstances beyond your control already decided your destiny? For thousands of years, this very question has intrigued and perplexed philosophers, scientists, and everyone who thinks deliberately about how they choose to live and act. The answer to this age-old riddle is universally relevant to our lives. The implications of our views on it can affect everything from small choices we make every day to our perspective on criminal justice and capital punishment. From the Stoics to Boethius, from Kant to Hume, from Sartre to contemporary philosophers, great minds have puzzled over this debate for centuries.