WHY WOULD IT BE GOOD IF A “THEORY OF EVERYTHING” EXISTED?

Greene, and Chalmers.^[180] To properly respond to this answer, we need to consider the proposition that the world is com­pletely intelligible. There are two ways to understand it.

One way is as an assumption about a “rational order” that exists in the world itself, whether or not we do or can know what this order is. Such a world is “explainable” whether or not we can discover the explanations. It might be held that such a world exists only if things that happen in the world are subject to laws, either universal or statistical. And, to add a TOE idea, the properties of and laws governing the most basic things in the universe explain (either universally or probabilistically) the properties and laws governing all other things in the universe. The world could be “intelligible” in this way whether or not we do or even can discover this “intelligibility”^[181]

The second way to understand the proposition that the world is completely intelligible is as saying that the world is completely intelligible to us—that we, or scientists, can achieve, or at least get closer to and approach, a complete understanding of the world. In both cases, “intelligibility” involves an idea of “correctness.” If the world is “intelligible”

252 | SPECULATION: WITHIN AND ABOUT SCIENCE in the first sense, then it is in fact subject to fundamental laws governing fundamental “atoms” correctly described by a TOE. And if it is “intelligible to us,” then we can come to know, or come closer to knowing, what these laws and “atoms” are and how everything is explained by them.^[182] We can come to know, or come closer to knowing, this “ra­tional order” (For the present, I will suppose this is what being “intelligible to us” requires; later, when I speak about “Newtonian intelligibility,” I will question that assumption.)

Why would it be a good thing if the universe were com­pletely intelligible in the unrelativized (“rational order”) sense? It might be said that a “rationally ordered” universe— one correctly described by a TOE—would be a good thing be­cause it would have an intrinsic beauty, simplicity, and unity.

My response is to say that, even if this is admitted, from a scientific perspective—from a perspective of what scientists and the rest of us seek from science—the existence of such a rational order would be a good thing only if we, or scientists, could come to know and understand this order by understanding the explanations given by that TOE. Knowledge and under­standing of the universe I take to be major goals of science. But suppose the fundamental laws of the TOE are too complex for us to understand.^[183] Or suppose they are not too complex for us to understand, but when we attempt to make a calculation from them that is needed to produce an explanation, we can't

do it. Laughlin and Pines offer an example of a quantum me­chanical equation relating charge and mass of electrons and atomic nuclei that covers many macro- and micro-bodies. In their critique of the idea of a TOE, they write:

However, it is obvious... that the Theory of Everything is not even remotely a theory of every thing.... We know this equation is correct........ However, it cannot be solved accurately

when the number of particles exceeds about 10. No computer existing, or that will ever exist, can break this barrier because it is a catastrophe of dimensions.⁵⁴

Nancy Cartwright⁵⁵ borrows an even simpler example from Otto Neurath, in which a thousand dollar bill is swept away by the wind and eventually falls to the ground; it is sub­ject to forces of gravity, wind, and friction. Even if we were able to cite (macro-) laws governing these forces, we are un­able to combine them and calculate where the bill will fall, and hence explain why it fell where it did.⁵⁶ Even if in some which flow all arrows of explanation, but we shall never learn what it is. For instance, it may be that humans are simply not intelligent enough to discover or to understand the final theory.” But readers should not de­spair, Weinberg adds, reassuringly, “my own guess is that there is a final theory, and we are capable of discovering it.” By contrast, Nagel seems to be asserting that if there is a final theory—if the world is completely intelligible—then it follows that we humans can discover this theory.

54. Laughlin and Pines, “Theory of Everything,” 28.

55. Nancy Cartwright, The Dappled World (Cambridge: Cambridge University Press, 1999), 26-27.

56. We might understand the forces and laws involved that determined where it landed. But I take it that this is not sufficient for (Nagelian) “com­plete intelligibility,” since we don't understand how these forces combine to determine where it landed.

abstract sense such a computation exists, we are unable to produce it. And if we were somehow able to succeed at this at the macro-level, suppose we could not compute a result from fundamental laws governing the basic “atoms.” TOE champions speak of computability (or “explainability,” or “in­telligibility”) in principle. But “in principle” has little signif­icance, at least in scientific pursuits, if in a straightforward, ordinary sense scientists can't accomplish or achieve this and don't care that they can't.^[184]

What I am suggesting is that “intelligibility” of the world in the unrelativized sense would be a “good thing,” as far as science is concerned, only if it is also intelligibility in the relativized sense. Otherwise, it becomes like God telling the suffering Job that the world is intelligible, just not to him or other humans. This may be comforting to Job and to others of faith, but it should not be to scientists seeking to understand the world. What they do and should care about is making the world intelligible to them (and to us). But if we relativize in­telligibility to what scientists, and perhaps the rest of us, do and should care about, then we need to consider not just what scientists and others can understand but also what they want to understand and with what depth and completeness they want to do so. In what follows, I will call this “Newtonian in­telligibility.” I do so not because Newton attempted to make things intelligible in terms of bodies, motions, and forces but because he attempted to make things intelligible in a way that needs to be viewed in terms of the problems he was trying to solve and the level at which he was trying to solve them.

The basic idea is that “completeness,” as far as intelligibility is concerned, is relative to context.

8.