To say what something is, is to do one or more of the following: (i) point out its defining properties—the essential properties unique to it; (ii) say what its essential parts are; and/or (iii)

point our minds’ eye directly to it.

A theory of X is a set of true propositions that that say what X is. (Or perhaps more accurately, someone who proposes a theory of X says what X is.)

A theory of everything, or TOE, is a theory that says what every single thing is! Of course, no one is capable of expressing a complete TOE. I doubt even the Anselmian God could do it: to express a complete TOE, God would have to express a theory about every expression of every theory, which would seem to entangle God in a vicious chase after his own chasing.

So we can only hope to give a partial TOE, one which says what some things are, but doesn’t say what everything is. Which things should we care to explain? That depends in part upon what you consider important. But I think we can say this much: a good partial TOE will describe the most fundamental things, such that our understanding of those things provides a helpful guide for understanding everything else. Here I’ll define ‘x is more fundamental that y’ to just mean that understanding what x is provides a guide for understanding more things than does understanding what y is. You might call this epistemic fundamentality, in contrast to varieties of ontological fundamentality. That isn’t to say that I’m not interested here in ontological fundamentality. I certainly am: indeed, epistemic fundamentality often tracks ontological fundamentality. It’s just that epistemic fundamentality will be my ultimate guide as to what to give a theory of.

Now suppose I have bunch of marbles on my desk. I wish to give a theory of them. I have a choice: I could either give a theory of each and every marble, or I could give a theory of the general kind, Marble (or perhaps a more specific kind like Marble on my Desk). I believe that a theory of Marble is more fundamental than a theory of particular marbles, since one wouldn’t know what a particular marble was without knowing what it is to be a Marble in general, whereas one could know what it is to be a Marble without knowing about particular marbles. Some philosophers see things the other way around: we first know particulars and then by certain mental acts of abstraction we come to know general kinds. I disagree (with fear and trembling). I believe we are directly acquainted with complexes of types and relations by virtue of which we can know what those types and relations are directly. From there we may come to know (or rationally infer) principles of instances of those types. At any rate, even if I’m wrong about that, there is still an important sense in which propositions about general kinds can guide our understanding of members of those kinds. So, a good partial TOE should say what the most fundamental, general kinds are.

I should point out a distinction between a higher-level property—that is, a property of a property—and a more general property. For example, being colorful is more general than being red. But being colorful isn’t a property of being red. The property of being a color is a property of being red, but the property of being colorful is not. Sometimes a higher-level property is also more general. For example, Being is the most general property and is also a property of every property. This can lead us to conflate these two ideas (as I think Aristotle might have). My TOE seeks to give an account of the most general kinds—moving from the more general to the more specific. It might be that ontological fundamentality goes the other way: more general properties get to be exemplified by virtue of their more specific determinates being exemplified. I’m not sure if that’s correct, but it’s something I’m open to.

Note: we’d fall into an undesirable infinite regress if we couldn’t know anything directly. For example, if I could only know x by first knowing x’s essential properties, then I couldn’t know those essential properties without first knowing the essential properties of those properties, and so on. Fortunately, I think we can and do know things directly. Indeed, I suspect that most of what we know is by direct awareness; learning is fundamentally a process of becoming aware of more things. So I see no methodological or epistemological problem with giving a partial TOE of the most fundamental kinds in principle.

A TOE in physics gives the most fundamental principles (laws or propositions) describing physical things and their relationships to each other, or the relationships between types of physical states. Although I think this is an important part of a TOE, it is incomplete. It leaves out things like propositions, relations, and kinds, like Physical Thing, Thing, and even the kind, Kind! None of these things are explained at all in a physical TOE. Therefore, although I’m very interested in physical TOEs and in the sciences that study physical things, I wish to have a more complete TOE, one which can help guide our understanding of everything, including non-physical things (like properties, sets, kinds, relations, propositions, and even TOEs themselves).

Therefore, I will give what I take to be a partial theory of everything by offering a theory of what I take to be the most general and most fundamental kinds there are. In saying what a kind is, I will do one or more of the following: (i) point out its defining properties—the essential properties unique to it; (ii) say what its essential parts are; and/or (iii) point our minds’ eye directly to it.

Some philosophers might call this ‘category theory’ because it is a theory of the most fundamental categories or kinds under which all things fall or could fall. However, I not only offer a hypothesis as to what these kinds are, but in many cases I propose additional fundamental axioms or principles (or hypotheses) about the kinds. For example, I propose what I take to be a refinement of the ZFC axioms for the kind, Set (I also offer an account of Set that is prior to these axioms). I see the project of spelling out in increasing detail and accuracy a theory of the most fundamental aspects of reality, including our very minds, to be the central project of truth seekers in general. So, I view this project not as one branch of philosophy, but rather as the as the central project of all truth-seeking. Thus, as a philosopher, I’m interested in gaining insights into the most fundamental aspects of reality, including aspects of knowledge, morality, the nature of aspects and natures themselves, and every other piece of reality under the sun.

I expect that my understanding will continue to grow and change as I continue to seek these matters out.