In Being and Essence: The Thomistic Doctrine on the Essence-Existence Distinction, Oscar Lawson provides a comprehensive exploration of one of the most pivotal concepts in Thomas Aquinas's philosophy: the distinction between essence and existence. Rooted in Aquinas's synthesis of Aristotelian metaphysics and Christian theology, this book delves into the profound implications of this distinction for understanding the nature of being, the divine, and the relationship between God and creation. The essence-existence distinction, according to Aquinas, offers a framework for reconciling the contingency of created beings with the necessity of God. Lawson traces the historical development of this doctrine, examining its origins in classical philosophy, its development in medieval scholasticism, and its influence on later metaphysical and theological discussions. With careful analysis of Aquinas's key works, including the Summa Theologiae and De Ente et Essentia, Lawson articulates how Aquinas's view of God as pure act of being (ipsum esse subsistens) shapes our understanding of creation, causality, and the very structure of reality. In addition to exploring the metaphysical dimensions of the essence-existence distinction, Lawson also addresses the theological implications, particularly how Aquinas's doctrine offers a coherent explanation of divine causality, the creation ex nihilo (creation from nothing), and the ultimate purpose of the world. The book situates Aquinas's thought within the broader context of the medieval intellectual tradition, engaging with contemporary critiques from philosophers like John Duns Scotus and William of Ockham, and tracing the legacy of the doctrine into modern and contemporary metaphysical debates. Being and Essence offers both a detailed analysis of Thomistic metaphysics and an accessible introduction to Aquinas's philosophical system, making it a valuable resource for students, scholars, and anyone interested in the intersection of philosophy, theology, and the nature of being. Through this exploration, Lawson illuminates how Aquinas's distinction between essence and existence continues to shape our understanding of the divine and the cosmos, offering a path to deeper reflection on the nature of reality itself.