Schelling's path-breaking 1809 treatise on freedom, the last major work published during his lifetime. The treatise is at the heart of the current Schelling renaissance--indeed, Heidegger calls it "one of the most profound works of German, thus of Western, philosophy." It is also one of the most demanding and complex texts in German Idealism. By tracing the problem of ground through Schelling's treatise, Mark J. Thomas provides a unified reading of the text, while unlocking the meaning of its most challenging passages through clear, detailed analysis. He shows how Schelling's implicit distinction between senses of ground is the key to his project of constructing a system that can satisfy reason while accommodating objects that seem to defy rational explanation--including evil, the origins of nature, and absolute freedom. This allows Schelling to unite reason and mystery, providing a rich model for philosophizing about freedom and evil today.