Common sense tells us all that things just do not pop into existence out of nothing. It takes work and effort to make things happen. Buildings are made by builders, diseases are the result of germs, headaches come from sinus pressure, plane crashes occur when there is some major malfunction, bumps occur in the middle of the night because of the wind blowing a shutter, an alley cat knocking over a trash can, or a burglar attempting a break-in.In other words, all of these assumptions about the world proceed on a principle. But what exactly is this principle? In our unreflective, intuitional, everyday speech, it goes something like "Things do not just happen 'out of the blue,' something has to make them happen!" In ancient and medieval times, the principle about which we are concerned was sometimes implicit, and other times explicit, albeit with various formulations, such as; "Nothing gives what it does not have," "There cannot be more in the effect than what was contained in the cause," "Whatever begins to exist must have a cause," or more frequently, ex nihilo nihil fit - "Out of nothing, nothing comes."In this work, I will propose that the principle of sufficient reason is the grand formulation of these intuitions and scholastic dictums, and thus is the principle that lies behind all of our casual inferences. Leibniz explicitly coined this term, yet he claimed not to discover any new principle, rather only to encapsulate all the implicit formulations used in the history of philosophy. The principle of sufficient reason is commonly formulated as such: "Every being has the sufficient reason for its existence (i.e., the adequate ground or basis in existence) either in itself or in another." Stated negatively, "Out of nothing, nothing comes" (being neither comes from nor can be determined by sheer nothing). The principle of sufficient reason, then, is simply an attempt to conveniently summarize, in one basic formula, the common intuitions of everyday life and what other great philosophers have either presupposed or loosely articulated in these more specialized formulas of the "principle of causality."Leibniz once said that without the principle of sufficient reason, very little in philosophy and science could be demonstrated. In a similar vein, the contemporary Thomistic philosopher, Norris Clarke, has called the principle of sufficient reason the dynamic principle of metaphysics, since it is in virtue of this very principle that enables the mind to pass from one being to another in order to make sense out of it: "All advance in thought to infer the existence of some new being from what we already know depends upon this principle."Using primarily, but not exclusively, the thought of St. Thomas Aquinas, the purpose of this book is to argue that there are good reasons for thinking that the principle of sufficient reason is true.

The Principle of Sufficient Reason (PSR) says that all contingent facts must have explanation. In this 2006 volume, which was the first on the topic in the English language in nearly half a century, Alexander Pruss examines the substantive philosophical issues raised by the Principle Reason. Discussing various forms of the PSR and selected historical episodes, from Parmenides, Leibnez, and Hume, Pruss defends the claim that every true contingent proposition must have an explanation against major objections, including Hume's imaginability argument and Peter van Inwagen's argument that the PSR entails modal fatalism. Pruss also provides a number of positive arguments for the PSR, based on considerations as different as the metaphysics of existence, counterfactuals and modality, negative explanations, and the everyday applicability of the PSR. Moreover, Pruss shows how the PSR would advance the discussion in a number of disparate fields, including meta-ethics and the philosophy of mathematics.

This monograph, The Knowledge of the First Principles in St. Thomas Aquinas, has a well-articulated vision of the issue addressed, both from the metaphysical and epistemological perspectives. It surveys the nature, roles, and habits of basic principles from the Thomistic view. It is a study directed towards a wise understanding of basic reality.

Metaphysics, formerly the queen of science, fell into oblivion under the onslaught of empiricism and positivism and its very possibllity came to be denied. Professor Elders traces the history of this process and shows how St. Thomas innovated in determining both the subject of metaphysics and the manner in which one enters this science, particularly in the framework of his Aristotle commentaries. The work then considers being and its properties, its divisions into being in act and being in potency, into the act of being essence, and into substance and the accidents. Finally the causes of being are considered. The work also introduces and surveys the extensive literature of Thomas interpretation of the past 50 years.

Cosmological reasoning is an important facet of classical arguments for the existence of God, but these arguments have been subject to many criticisms. The thesis of this book is that Thomas Aquinas can dodge many of the classic objections brought against cosmological reasoning. These objections criticize cosmological reasoning for its use of the Principle of Sufficient Reason; its notion of existence as a predicate; its use of ontological reasoning; its reliance on sense realism; its ignoring of the problem of evil; and its susceptibility to the critique of "ontotheology" as famously put forward by Heidegger. Secondly, the book proposes that the kind of reasoning found in Aquinas's De Ente can be formulated in a more robust version. Prompted by Aquinas’s admissions that philosophical knowledge of God is the prerogative of metaphysics, the second main portion of the book extensively illustrates how the more robust version of the De Ente is the interpretive key for Aquinas’s many arguments for God. Hence, the book should be of interest both to philosophers engaged in cosmological reasoning discussion and to Thomists interested in understanding Aquinas’s viae to God. Finally, the deep purpose of the book is to reawaken interest in Thomistic Existentialism, an interpretation of Aquinas that flourished in the 1950's in the works of Etienne Gilson, Jacques Maritain, and Joseph Owens. In this interpretation, a particular thing’s existence is the actuality of the thing in the sense of a distinctive actus not translatable into something else, for example, the fact of the thing or the thing having form. This book clearly explains how this interpretation looks at Thomas's metaphysics, and why it helps illuminate metaphysical realities.

When it is taught today, metaphysics is often presented as a fragmented view of philosophy that ignores the fundamental issues of its classical precedents. Eschewing these postmodern approaches, W. Norris Clarke finds an integrated vision of reality in the wisdom of Aquinas and here offers a contemporary version of systematic metaphysics in the Thomistic tradition. The One and the Many presents metaphysics as an integrated whole which draws on Aquinas' themes, structure, and insight without attempting to summarize his work. Although its primary inspiration is the philosophy of St. Thomas himself, it also takes into account significant contributions not only of later philosophers but also of those developments in modern science that have philosophical bearing, from the Big Bang to evolution.