To: Ryan S.
From: Geoffrey Klempner
Subject: Abstract and concrete objects
Date: 9 April 2001 11:31

Dear Ryan,

Thank you for your e-mail of 30 March, with your first essay for the Metaphysics program in response to the question, 'Give everyday examples illustrating the distinction between 'abstract' and 'concrete' objects, and also between 'possible' objects and 'actual' objects. What philosophical questions arise from this four-fold classification?'

This is an impressive first effort. I liked the way you took a stand, refusing to allow that possibilities, as you call them, can be 'objects' falling side-by-side with actual objects under the general heading, 'Objects'.

One relatively small point. 'Possible objects are those that don't exist' is not strictly true. Actual objects had better also be possible. However, we can fix this up by stipulating that 'possible'='possible but not actual'.

Of course, the suspicion remains that the dispute here is merely verbal. According to you, possibilities, or 'possibilia' as they are sometimes called, are different from actual objects, not only in not being actual but also in not being 'objects'. What's to stop a philosopher simply coining a term, 'schmobjects', which includes under it possibilia and actual objects? In other words, what we are looking for here is more than just a disinclination, however well motivated, to use a certain word. Biologists object to the popular, loose usage which classifies whales as 'fish'. We understand what is at stake here. 'Whales are not fish' expresses an significant discovery about the natural world.

One theory we have to reckon with is the view of David Lewis that possible worlds are every bit as 'real' as the actual world. The difference is merely one of local perspective. Now, there might be all sorts of objections to this theory on the grounds of metaphysical extravagance. But it would seem a strange objection to deny that the 'possible objects' that exist in a world similar to ours in which, e.g. Germany won the Second World War are not 'objects' at all. These entities, or schmobjects, have reality, they exist in that possible world. So far as we are concerned, however, they are not 'objects'.

Taking David Lewis' view alters the proposed classification somewhat. Under the general heading 'possible objects', we now have 'possible objects which are also actual' and 'possible objects which are non-actual'.

If we define 'object' as 'something that can be referred to' then there is a problem about possibilia, namely, the Quinian objection that you can never, in principle, narrow down your description sufficiently to pick out just one 'possibilium'. However, that objection rests on the assumption that the existence of something is conditional on the possibility of our being able to refer to it. That general principle can't be right, because we have learned from mathematics that there are so-called 'irrational numbers' which cannot be referred to. (To refer to a real number which cannot be expressed as a rational number, i.e. a fraction, would involve specifying an infinite number of decimal places.)

There are issues which you don't raise, which you might think about. What do we say about colours? Is red a concrete or abstract object? That seems to turn on the question whether there would still exist 'red' if all red objects in the universe were destroyed. Does that case indicate that the borderline between concrete and abstract objects might be a little fuzzy, perhaps? You confidently assert that forces, energies, gravity etc. are concrete. It is one thing to assert that concrete objects have certain *powers*, e.g. the power of a magnet to attract iron filings, but quite another to assert that a magnetic field is itself an 'object'.

Since the work of Kripke (see his book 'Naming and Necessity') philosophers would be a lot more cautious about asserting the existence of concepts under which no objects actually fall. They would argue that a term such as 'unicorn' has the function of a natural kind concept, like 'horse' or 'shark' or 'whale'. Yet it lacks one crucial element of a natural kind, viz. being based on reference to something that actually exists. We discover things about 'horses', 'sharks', 'whales'. Our concept of a 'horse' is of 'whatever is similar to such-and-such specimens, according to the best biological classification'. Lacking specimens of unicorns, we don't have a determinate concept, but merely a few properties thrown together ad hoc. 'Take a horse, add a horn, add the power to detect virgins, etc'. Unicorns lack a 'real essence', in Locke's sense.

As you can see, I am looking for things to pick on. But overall you have produced a fine, well argued piece of work. Well done!

All the best,

Geoffrey