Socrates' search is for direction in life, for how one should live. For him, an unexamined life is not worth living. The suggestion in this thesis is that Plato follows Socrates in asking the extremely relevant and practical question that seeks to discover the sort of life worthy of the human individual. For Plato, the answer involves the pursuit of knowledge and wisdom, it is, in short, to do philosophy. Socrates regards genuine philosophy as active and dialectical. Plato accepts the challenge of conveying this through the written word. Implicit in his dialogues is the idea that human wisdom is a fusion of the spiritual and the rational. The philosophic life is realised in practice by following the three interdependent ways of the philosopher, these are the ways of dialectics, death and love. These identify the philosophic life with a critically detached, yet passionate attitude to the world. However, this practical teaching is guided and informed by Plato's metaphysics, in particular his idea of the Good. A major task of this thesis is to show how the idea of the Good is relevant to ordinary human conduct.

There is a debate in the philosophy of time over the status of non-present entities. Do these things exist, and if so, what sorts of things are they? Recently, the debate has split into two groups, presentists and eternalists. Presentists hold that no past or future things exist now. Socrates does not now exist, though he did in the past; my future daughter does not now exist, though she may in the future. Ontologically, the present is distinct, serving to demarcate all that currently has existence. As far as the eternalist is concerned, all entities - whether past, present, or future - are equally real. If it was, is, or will be, it can be found in the eternalist picture of time. As such, there is no distinct present at which some entities exist while others do not; rather, everything enjoys the same ontological status. I will be concerned to offer an assessment of the presentist view. Common objections against presentism will be examined, amplified, and answered where appropriate. I will not examine the arguments in favor of the presentist view. Rather, I wish to describe why it is that the eternalist feels compelled to deny presentism. Ultimately, my goal will be to show that although presentism survives some of the current objections raised against it, it does not survive them all. Presentism is an interesting, but ultimately unsatisfactory view. There is a modified form of presentism (call it presentism*) that can meet the objections raised against the original position, and after noting some of the objections raised against presentism, I will sketch the outlines of presentism* in some detail. I intend to show that presentism* is able to retain what is most valuable about presentism, while also withstanding certain objections that the latter view could not.

When considering the nature of the human being, Descartes holds two main claims: he believes that the human being is a genuine unity and he also holds that it is comprised of two distinct substances, mind and body. These claims appear to be at odds with one another; it is not clear how the human being can be simultaneously two things and one thing. The details of Descartes' metaphysics of substance exacerbates this problem. Because of various theological and epistemological commitments, Descartes frames his metaphysics of substance in a way that ensures mind and body's real distinction from one another. Articulated from this perspective, the problem becomes one wherein it is not clear that two completely separate substances can come together to form one entity. The aim of this thesis is to show how Descartes can hold real distinction and true union without contradiction. To this end, I will first detail the problem and outline a variety of solutions that have already been presented. Then I will outline important concepts relating to Descartes' metaphysics of substance and attributes. This not only reveals the depth of the problem but also lays the groundwork for my proposed solution. I argue that the key to understanding how these two claims are consistent and in accord with Descartes' philosophy is through a comment Descartes makes to his contemporary Henricus Regius where he urges that the union of mind and body is achieved through a "mode of union." I substantiate this claim by arguing for the intelligibility of understanding union as a modal attribute within Descartes' framework. Finally, I show how Descartes can hold real distinction and true union with consistency. When union is understood as a mode, mind and body are able to exist apart from one another, ensuring real distinction. Moreover, union construed as a mode does not allow the complete separability of mind and body. Thus, when united, mind and body achieve the kind of unity Descartes desires for the human being.

The Simplest Quantified Modal Logic (SQML) is controversial because it seems to conflict with some of our most basic intuitions about what is possible and what is necessary. Two controversial principles, the Barcan Schema (BS) and Necessary Existence NE, are valid in SQML models. Informally expressed, BS requires that, if it is possible that something is F, then there is something that is possibly F. This result seems to conflict with the intuition that there is some property F such that F could have been exemplified, though is not possibly exemplified by any existing thing. NE conflicts with the intuition that there could have been more/different existents than there actually are and the intuition that those things that actually exist could have failed to exist. The primary goal of this thesis is to provide a semantics for SQML that justifies the validity of BS and NE with these intuitions in mind. This is the focus of the fifth section of the thesis. In the first four sections of the thesis, I discuss prior attempts to meet my primary goal, all of which I consider unsuccessful. According to my view, which I call M-combinatorialism, the world is comprised of simples, mereological sums of those simples and universals that the former objects exemplify. I argue that we can justify the validity of BS by appealing to these facts about simples and sums: (1) simples are arranged such that the sums of these simples exemplify certain properties, (2) the actual arrangement of any given number of simples is a contingent matter and (3) had the simples that are actually arranged to form the complex objects in the actual world been arranged differently, the sums of these simples could have exemplified radically different properties. Insofar as Combinatorialists construct all possible individuals only out of actual individuals, they are committed to the necessary existence of those actual individuals, which allows the M-Combinatorialist to justify the validity of NE. So, the M-Combinatorialist is able to provide an adequate semantics for SQML. In the final section, I defend my view against objections.

Title from title page of PDF (University of Missouri--St. Louis, viewed Febuary 22, 2010). Includes bibliographical references (p. 37-39).

In this dissertation, I defend the claim that realism – that is, a theory committed to an ontology of universals and particulars – is a more viable theory than any of the others adopted in order solve to the problem of universals. I begin in chapter 1 by setting out a method for comparing the various theories offered as solutions to this problem that is based primarily on a preference for those theories that exhibit greater ontological parsimony. In developing this method I endorse rather than reject (as is standard for realists to do) Quine’s criterion of ontological commitment. In chapter 2, I utilize the aforementioned method of theory comparison to argue for the greater comparative viability of realism over each of its primary competitors. In chapter 3, I set out and offer a solution to the “problem of instantiation”, which has traditionally been taken to be the most difficult problem for realists to solve. Finally, in chapter 4, I discuss two remaining issues that face the sort of “Quinean” realism that I prefer: (1) the ability of this version of realism to accommodate the traditional realist distinction between universals and particulars, and (2) the ability of this version of realism to account for “relational facts” while maintaining its greater comparative viability over its competitors. / text

Since the linguistic turn, many have taken semantics to guide metaphysics. By examining semantic theories proposed by philosophers and linguists, I argue that the semantics of a true theory in a natural language can serve as only a partial guide to metaphysics. Semantics will not always lead to determinate answers to questions of the form 'Does theory T carry an ontological commitment to Fs?' Further, semantics will never deliver answers to questions regarding the nature of Fs. If semantics is to be our guide, we must look to our best semantic theories to determine whether a theory carries ontological commitments to Fs. I develop criteria to determine when a semantic treatment is semantically adequate and should be counted amongst our best theories. Given these criteria, there can be more than one empirically adequate semantic treatment of a natural language theory. To determine ontological commitments I appeal to Quine's Criterion, which states that a theory has Fs in its ontology just in case it says or entails that there are Fs. To determine what a theory says and entails, we must appeal to semantic treatments. Since different equally adequate semantic treatments can yield different contents and entailments, Quine's Criterion delivers ontological commitments only relative to a semantic treatment. I then argue for a supervaluationist principle that delivers unrelativized, but possibly indeterminate, ontological commitments of a theory. Next, I apply my methodology to two case studies which exemplify two kinds of answers the supervalutationist principle might deliver concerning ontological commitments. I argue through an examination of data and formal treatments that plural expressions carry indeterminate ontological commitments to summed entities, while collective nouns carry determinate ontological commitments to group-like entities. Finally, I undertake an examination of what groups, things like teams, committees and courts, might be that accords with the minimal verdict delivered by the semantics of collective noun -- that they exist -- but which goes beyond this to examine their nature. I assess and reject the views of groups currently on offer and propose and defend a novel view of groups as realizations of structures. / text

It is widely agreed that ontological reduction is possible, that the ontology of one theory can be shown to be nothing over and above the ontology of a distinct theory. However, it is also widely agreed that one assesses a theory’s ontology by determining what it says there is. I show that there is a tension between these orthodox positions. To resolve this tension, I propose and defend the view that the ontological commitments of a statement are sensitive to the theory in which it is embedded. / text

This dissertation consists of two parts. Part I proposes a new approach to modality, abductive modal realism. Part II proposes a new version of physicalism, abductive physicalism. The parts relate in that abductive physicalism presupposes abductive modal realism.Abductive modal realism holds that inference to the best explanation (i.e. abduction) grounds some and any justified belief about mind-independent necessity and possibility. This approach avoids the disadvantages of extant approaches to modality. Specifically, unlike extant approaches, abductive modal realism accepts real, mind-independent necessities and possibilities without employing a modal epistemology that fits these poorly. Abductive physicalism holds that we should adopt abductive modal realism, that abduction favors physicalism, and thus, that we should adopt physicalism. Although standard a posteriori physicalism accepts the latter claims, it sees appeals to abduction as exceptions to an otherwise non-abductive modal epistemology. Abductive physicalism, contrariwise, sees abduction as the arbitrator of modal disputes quite generally. This difference allows abductive physicalism to avoid problems that plague standard a posteriori physicalism.

There is a debate in the philosophy of time over the status of non-present entities. Do these things exist, and if so, what sorts of things are they? Recently, the debate has split into two groups, presentists and eternalists. Presentists hold that no past or future things exist now. Socrates does not now exist, though he did in the past; my future daughter does not now exist, though she may in the future. Ontologically, the present is distinct, serving to demarcate all that currently has existence. As far as the eternalist is concerned, all entities - whether past, present, or future - are equally real. If it was, is, or will be, it can be found in the eternalist picture of time. As such, there is no distinct present at which some entities exist while others do not; rather, everything enjoys the same ontological status. I will be concerned to offer an assessment of the presentist view. Common objections against presentism will be examined, amplified, and answered where appropriate. I will not examine the arguments in favor of the presentist view. Rather, I wish to describe why it is that the eternalist feels compelled to deny presentism. Ultimately, my goal will be to show that although presentism survives some of the current objections raised against it, it does not survive them all. Presentism is an interesting, but ultimately unsatisfactory view. There is a modified form of presentism (call it presentism*) that can meet the objections raised against the original position, and after noting some of the objections raised against presentism, I will sketch the outlines of presentism* in some detail. I intend to show that presentism* is able to retain what is most valuable about presentism, while also withstanding certain objections that the latter view could not.