.1. Different conceptions of ontology
As a first approximation, ontology is the study of what there is. Many classical philosophical problems are problems in ontology, like the question whether or not there is a god, or the problem of the existence of universals. These are all problems in ontology in the sense that they deal with whether or not a certain thing, or more broadly entity, exists. But ontology is usually also taken to encompass problems about the most general features and relations of the entities which do exist. There are also a number of classic philosophical problems that are problems in ontology understood this way. For example the problem how a universal relates to a particular that has it (assuming there are universals and particulars), or the problem how an event like John eating a cookie relate to the particulars John and the cookie, and the relation of eating, assuming there are events, particulars and relations. These kinds of problems quickly turn into metaphysics more generally, which is the philosophical discipline that encompasses ontology as one of its parts. The borders here are a little fussy. But we have at least two parts to the overall philosophical project of ontology: first, say what there is, what exists, what the stuff is reality is made out off, secondly, say what the most general features and relations of these things are.
This way of looking at ontology comes with two sets of problems which leads to the philosophical discipline of ontology being more complex than just answering the above questions. The first set of problems is that it isn't clear how to approach answering these questions. This leads to the debate about ontological commitment. The second set of problems is that it isn't so clear what these questions really are. This leads to the philosophical debate about meta-ontology. Lets look at them in turn.
One of the troubles with ontology is that it not only isn't clear what there is, it also isn't so clear how to settle questions about what there is, at least not for the kinds of things that have traditionally been of special interest to philosophers: numbers, properties, god, etc. Ontology is thus a philosophical discipline that encompasses besides the study of what there is and the study of the general features of what there is also the study of what is involved in settling questions about what there is in general, especially for the philosophically tricky cases. How we can find out what there is isn't an easy question to answer. It seems simple enough for regular objects that we can perceive with our eyes, like my house keys, but how should we decide it for such things as, say, numbers or properties? One first step to making progress on this question is to see if what we believe already rationally settles this question. That is to say, given that we have certain beliefs, do these beliefs already bring with them a rational commitment to an answer to such questions as ‘Are there numbers?’ If our beliefs bring with them a rational commitment to an answer to an ontological question about the existence of certain entities then we can say that we are committed to the existence of these entities. What precisely is required for such a commitment to occur is subject to debate, a debate we will look at momentarily. To find out what one is commited to with a particular set of beliefs, or acceptance of a particular theory of the world, is part of the larger discipline of ontology.
Besides it not being so clear what it is to commit yourself to an answer to an ontological question, it also isn't so clear what an ontological question really is, and thus what it is that ontology is supposed to accomplish. To figure this out is the task of meta-ontology, which strictly speaking is not part of ontology construed narrowly, but the study of what ontology is. However, like most philosophical disciplines, ontology more broadly construed contains its own meta-study, and thus meta-ontology is part of ontology, more broadly construed. Nonetheless it is helpful to separate it out as a special part of ontology. Many of the philosophically most fundamental questions about ontology really are meta-ontological questions. Meta-ontology has not been too popular in the last couple of decades, partly because one meta-ontological view, the one often associated with Quine, has been accepted as the correct one, but this acceptance has been challenged in recent years. One motivation for the study of meta-ontology is simply the question what question ontology aims to answer. Take the case of numbers, for example. What is the question that we should aim to answer in ontology if we want to find out if there are numbers, that is, if reality contains numbers besides whatever else it is made up from? This way of putting it suggest an easy answer: ‘Are there numbers?’ But this question seems like an easy one to answer. An answer to it is implied, it seems, by trivial mathematics, say that the number 7 is less than the number 8. If the latter, then there is a number which is less than 8, namely 7, and thus there is at least one number. Can ontology be that easy? The study of meta-ontology will have to determine, amongst others, if ‘Are there numbers?’ really is the question that the discipline of ontology is supposed to answer, and more generally, what ontology is supposed to do. We will pursue these questions below.
The larger discipline of ontology can thus be seen as having four parts:
- (O1) the study of ontological commitment, i.e. what we or others are committed to,
- (O2) the study of what there is,
- (O3) the study of the most general features of what there is, and how the things there are relate to each other in the metaphysically most general ways,
- (O4) the study of meta-ontology, i.e. saying what task it is that the discipline of ontology should aim to accomplish, if any, how the question it aims to answer should be understood, and with what methodology they can be answered
