Howard Peacock

This thesis argues for realism about universals —the view that, in addition to particular things, there exist universals instantiated by those particular things. The first half presents a positive case for realism. Here it is claimed that universals are needed in our ontology to serve as the respects in which things are the same, and the features or characteristics that things have in common.This argument is defended against nominalist responses, first, that our apparent ‘ontological commitment’ to features and characteristics is not genuine; and second, that the same theoretical work can be achieved by treating respects of sameness as sets of particulars or sets of tropes rather than sui generis universals.The second half of the thesis defends the realist against the most serious objections to an ontology of universals. These are the problems arising from the realist’s obligation to ascribe referential function to predicates, and the family of difficulties known as ‘‘Bradley’s Regress’’. By addressing both the reasons to believe in universals, and the alleged reasons not to believe in universals, it is hoped that a coherent case for realism is achieved

There are two different ways of understanding the notion of ‘ontological commitment ’. A question about ‘what is said to be’ by a theory or ‘what a theory says there is’ deals with ‘explicit’ commitment ; a question about the ontological costs or preconditions of the truth of a theory concerns ‘implicit’ commitment. I defend a conception of ontological commitment as implicit commitment, and argue that existentially quantified idioms in natural language are implicitly, but not explicitly, committing. I use the distinction between the two kinds of ontological commitment to diagnose a flaw in a widely used argument to the effect that existential quantification is not ontologically committing

Bradley's Regress-a problem about what grounds or 'accounts for' the ability of two or more things to stand in a relation-is often presented as a problem about truthmakers: what entity 'makes it true' that two objects a and b are related? I criticize this account of the regress on the grounds that it is dialectically weak and trivially solvable. I then propose an alternative interpretation, according to which the regress challenges our ability to use relational entities to give an account of the underlying metaphysical situation in cases of relatedness. Although I concede that this regress is fatal for some realist and trope-theoretic accounts of relatedness, and does not permit of a trivial solution, I suggest a way we can avoid it without giving up an ontology of relational universals or relational tropes. Bradley's Regress-correctly understood-sets limits on our theory of relations; it does not force us to abandon relations altogether.

Abstract: It is often claimed that realists about universals must be either “platonists,” holding that universals lack spatio-temporal location, or “aristotelians,” asserting that universals are located where their instances are. What’s more, both camps agree that locatedness or unlocatedness is part of the essential nature of universals; consequently, aristotelians say that universals cannot exist un located, and platonists allege that universals cannot be located. Here I argue that the dispute may be resolved by synthesizing the most attractive features of each position. I claim that universals are located at their instances when instantiated by particulars which themselves possess a spatio-temporal location; however, un instantiated universals exist without location. This has the consequence that it will often be a contingent matter whether a given universal has a location, if the universal is only contingently instantiated. Nevertheless, I claim, objections to this position may be overcome.

The mere fact that ontological debates are possible requires us to address the question, what is it to claim that a certain entity or kind of entity exists—in other words, what do we do when we make an existence-claim? I develop and defend one candidate answer to this question, namely that to make an existence-claim with regard to Fs is to claim that we can refer to Fs. I show how this theory can fulfil the most important explanatory desiderata for a theory of existence; I also defend it against the charges of illegitimate ‘semantic ascent’ and of making existence counterfactually dependent on human linguistic ability.

Whereas traditional nominalists accept the realist's challenge to solve a 'Problem of Universals', the Ostrich Nominalist responds that there is no such Problem to answer. I suggest that Ostrich Nominalist arguments expose a genuine flaw in the realist project. However, I argue, Ostrich Nominalism is ultimately defeated by a problem about the analysis of qualitative sameness and difference. Qualitative sameness and difference are adequately understood only as sameness or difference in some respect. The need to say what these respects of sameness and difference are (if not universals) constitutes a genuine Problem of Universals; consequently—I claim—the Ostrich Nominalist is mistaken.

The problem of the ‘Unity of the Proposition’ is the problem of explaining the difference between a content-expressing declarative sentence and a ‘mere list’ of referents. The prevailing view is that such a problem is to be solved metaphysically, either by reducing our ontology to exclude propositions or universals, or by explaining how it is possible for a certain kind of complex entity – the ‘proposition’– to ‘unify’ its constituents. I argue that these metaphysical approaches cannot succeed; instead the only viable approach is linguistic, identifying features of the (type–) sentence itself that enable it to express a content. Thus the problem of the ‘Unity of the Proposition’ (distinguishing sentences from lists) is distinct from the problem of ‘propositional unity’ (explaining how the constituents of propositions form a unified content). I suggest that, while the latter problem is not pressing, the former does not permit of an answer which applies in generality in all languages; we can only fully explain the Unity of the Proposition for single languages or groups of similar languages.