This book revisits four early-modern debates of Reformed theology concerning the will of God. Reformed scholasticism advocated a particular relationship between divine knowledge, will, and power, which was altered by Jesuits, Remonstrants, Descartes, and Spinoza. In all these debates modal categories like contingency and necessity play a prominent part. Therefore, these positions are evaluated with the help of modern modal logic including possible world semantics. The final part of this study presents a systematic defense of the Reformed position, which has been charged of theological determinism and of making God the author of sin. In modern terms, therefore, the relation of divine and human freedom and the problem of evil are discussed.