The ontological argument for the existence of God has enjoyed a recent renaissance among philosophers of religion. Alvin Plantinga's modal version is perhaps the most notable example. This essay critically examines Plantinga's rendition, uncovering both its strengths and weaknesses. The author concludes that while the argument is probably formally valid, it is ultimately unsound. Nonetheless, Plantinga's version has generated much interest and discussion. The author spends some time uncovering the reasons for the argument's powerful intuitive appeal. He concludes his essay (...) by appraising Pruss's recent defence of Plantinga's argument. (shrink)

In this paper, the author develops a theory of concepts and shows that it captures many of the ideas about concepts that Leibniz expressed in his work. Concepts are first analyzed in terms of a precise background theory of abstract objects, and once concept summation and concept containment are defined, the axioms and theorems of Leibniz's calculus of concepts (in his logical papers) are derived. This analysis of concepts is then seamlessly connected with Leibniz's modal metaphysics of complete individual concepts. (...) The fundamental theorem of Leibniz's modal metaphysics of concepts is proved, namely, whenever an object x has F contingently, then (i) the individual concept of x contains the concept F and (ii) there is a (counterpart) complete individual concept y which doesn't contain the concept F and which `appears' at some other possible world. Finally, the author shows how the concept containment theory of truth can be made precise and made consistent with a modern conception of truth. (shrink)

In this dissertation, I develop an interpretation of Leibniz on modality and free will. I do so for two reasons: first, I am attempting to revitalize the notion that Leibniz is the predecessor of contemporary modal semantics; second, I am using Leibniz's philosophical system to motivate responses to contemporary philosophical issues in modality and free will. In Chapter One, I argue that Leibniz's basic principles are plausible theoretical tools that ought to be used by contemporary philosophers in developing their philosophical (...) systems. In Chapter Two, I develop Leibniz's views on the nature of individuals. I argue that possible individuals are actually of the same sort as individuals in the actual world--possible individuals and actual individuals are complete creatures that do not differ ontologically from each other. In Chapter Three, I argue that Leibniz's views on possible individuals make him a modal realist and compare his view with contemporary modal realism in order to support this claim. I also argue that counterparts avoid many of the problems set for them by contemporary thinkers; I end with the ways that Leibniz's view differs from contemporary accounts. In Chapter Four, I argue that Leibniz provides two different analyses of modality. The first is an infinite analysis account; the second is a possible worlds account. I argue that these two accounts are compatible and amount to two different descriptions of the same theory of modality. I address objections to each account in order to show this. In Chapter Five, I argue that Leibniz is a compatibilist about free will. Importantly, I argue that it is precisely Leibniz's account of modality that allows for this compatibilism, as against a necessitarian like Spinoza. I then use Leibniz's account to challenge contemporary libertarians about free will on the basis of the principle of sufficient reason. I also show how Leibniz can help semicompatibilism avoid a worry concerning necessitarianism. At the end of the day, I claim that adopting elements of Leibniz's system can help us better understand modality and the freedom of the will and can be an aid in furthering contemporary philosophical theory. (shrink)