From bundles to bare particulars and back again

Here's a compelling narrative. Start with the bundle theory of substance: substances are nothing but bundles of properties. Then observe that this suffers from serious problems. If a substance is nothing but a bundle of properties, it is unclear how a substance could have had other properties than it does. Further, intuitively it should be possible to have two indiscernible substances--ones with all the same properties. This motivates a move to bare particular theory. According to bundle theory, substances were constituted by one kind of thing: properties. Bare particular theory makes substances be constituted by both properties and a special entity, the bare particular. Introducing the bare particular solves the modal problem, since we can say that the identity of substances is grounded in the identity of the bare particulars, so you can have a substance in one world with different properties than the very same substance in another world, as long as the same bare particular is found in both. Further, there is no difficulty with indiscernibles, as long as you have two bare particulars.

Note that this narrative isn't quite the standard narrative about bare particulars. The standard narrative introduces bare particulars to solve the problem of predication, by making the bare particular be the subject of predication. That standard narrative, however, falls prey to a problem that Andrew Bailey points out: we don't want to say that the bare particular has the ordinary properties of the host substance (for then we get reduplication), but if it does not, then it's not the subject of predication.

So let's stick to my from-bundles-to-bare-particulars narrative. But at this point there is a really interesting move possible, one that was pointed out in my undergraduate metaphysics class by a brilliant freshman, Rose Brugger. According to bare particular theory, substances are constituted by two kinds of things: properties and a bare particular. But Brugger suggested that we take the bare particular to just be an individuating property. Namely, a haecceity.

The result is a really interesting theory. It is a kind of bundle theory. However, first, the motivations for bare particular theory continue to be satisfied: we can ground identity between substances in identity of the haecceity. Second, we solve the puzzle of the mysterious "bareness" of the bare particular: the haecceity isn't some weird propertyless individual, but just a property, albeit a special one. Third, the resulting theory is more parsimonious, because it posits one fewer fundamental category: all it needs are substances and their constituent properties, without a separate category of bare particulars.

The resulting theory is superior to both standard bundle theory and standard bare particular theory, being only slightly more complex than standard bundle theory but solving a number of problems.