When people are talking about metaphysics, they are usually talking about ontology, or the question of what exists. This post is mostly about ontology as part of metaphysics. However, I used “metaphysics” rather than “ontology” in the title, because I think that there is a role for ontology. But, I see that role as calling for a different conception of ontology, such that it should not be part of metaphysics.
The trouble with ontology as metaphysics (or with metaphysical ontology, as I shall term it), is that it doesn’t actually matter what exists. Maybe elves exist, but we have no access to them or to whatever it is that they do. And in that case, having elves in our ontology (our list of what exists) serves no purpose. On the other hand, maybe electrons don’t exist and gravitational fields don’t exist (as the anti-realists have been arguing). But even if those don’t exist, we want to have them on our list of things because our science has a lot to say about them.
In short, it seems to me that ontology, taken as a branch of metaphysics, seeks to answer questions that cannot be answered, and for which the answers would be useless to us even if they could be answered.
My suggestion is that we should ignore the question of what exists. Instead, we should look at the question of what is important enough for us to single out and name, and important enough for us to reference. For it is those things that we name, and reference in useful ways, that become a basis for our knowledge.
Epistemic ontology, then, should be a study of what is important enough for us to name and to reference. And it should also study why those entities are important, and how we single them out so that we are able to recognize them.
Even if elves actually exist, they don’t belong in our epistemic ontology, because they are useless to us except in stories that we recognize as fictional and use for entertainment. On the other hand, even if the anti-realists are correct that electrons and gravitational fields do not exist (except as abstract ideas), they belong in our epistemic ontology because they are both important and useful to our science.
Most of us would agree that emeralds exist in a metaphysical sense. However, as suggested in my “Just So” story about emeralds (and elaborated in a post on induction), there might be societies that would use emeralds as paving gravel, just the way that they use other small stones. For such a society, emeralds would have no relevance. They would not belong as part of the epistemic ontology of such a society, even though they exist.
Quine, in discussing the indeterminacy of translation and the inscrutability of reference, has used the made up word “gavagai” to illustrate his point. Suppose a linguist, studying a previously unknown language, hears “gavagai” being used in the presence of rabbits. Quine raises the question of whether the evidence available to the linguist would enable him to decide if gavagai means rabbit or undetached rabbit parts or rabbit stage. See the Wikipedia entry for more details.
Presumably what gavagai means, would be what that particular society or culture thought important enough to single out and name. So what gavagai refers to is whatever that culture would have as part of its epistemic ontology.
I have explained why I think that ontology, taken as part of metaphysics, is not what we need. And I have suggested an alternative reconception of ontology as part of epistemology.