Why Does the World Exist: An Existentia - By Jim Holt Page 0,110

to be so disappointingly average: an indifferent mixture of good and evil, of beauty and ugliness, of causal order and random chaos; inconceivably vast, yet falling well short of the full cornucopia of possible being. Reality is neither a pristine Nothing nor an all-fecund Everything. It’s a cosmic junk shot.

Such was the conclusion that I had teased out of Parfit’s scheme. But, frustratingly, it still fell short of being a complete explanation. If Simplicity did indeed rule at the highest level, did this merely happen to be true? What about rival meta-Selectors, like Fullness? (I had put a question mark under it on my diagram.) And what if there were no meta-Selector at all? (Another question mark on my diagram.) Was the most general explanation of reality doomed to end with an inexplicable brute fact?

Parfit had done his bit. He had dispelled much of the fog surrounding the mystery of existence. And he had given me a very nice lunch in the bargain. It was time for him to return to his study, where he would reimmerse himself in questions of moral philosophy, of values and desires and reasons. And it was time for me to leave the rarefied cloister of All Souls and return to the rude world of Vile Bodies.

I thanked Parfit effusively, saw myself to the college gate, and turned onto the High Street, whose shadows were lengthened by the late-afternoon sun.

A WEEK LATER I was back in New York, still vexing over the now-crumpled diagram I had shown to Parfit. Then, walking one evening in the tonic squalor of the East Village, a million miles from All Souls, I had an epiphany. The last piece of logic snapped into place. I had the proof.

Epistolary Interlude

The Proof

Wednesday morning

2 Fifth Avenue, New York

Dear Professor Parfit,

It was so nice spending the afternoon with you at All Souls. In reflecting on our conversation, I think I may have hit upon a complete and unique explanation for the most general form reality takes—an explanation that finally resolves the question, Why is there something rather than nothing?

I begin by assuming two principles:

(I) For every truth, there is an explanation of why it is true.

(II) No truth explains itself.

The first of these, of course, is what Leibniz called the Principle of Sufficient Reason. It says that there are no brute facts. I take Sufficient Reason to be not so much a truth in itself, but rather a provisional guide to inquiry, one that says, “Always look for an explanation unless you find yourself in a situation where further explanation is impossible.”

The second principle is a more general version of your point that no Selector can select itself. It is meant to rule out circularity. A cause cannot cause itself. A rationale cannot justify itself. God cannot create himself. A set cannot be a member of itself. In set theory, this is called the Axiom of Foundation. So I’ll call principle (II) “Foundation.”

Now here’s the argument that there is one, and only one, complete explanation for the form that reality takes.

At level 0, the level of reality, you have all the “cosmic possibilities” for how reality might have turned out. These range from the Null possibility to the All Worlds possibility, and they include every one of the countless intermediate possibilities, where some conceivable worlds of some types exist, but not others. One of these cosmic possibilities has to obtain, as a matter of logical necessity. Call the cosmic possibility that actually does obtain A, for “actual.”

At level 1, the lowest explanatory level, you have all the plausible Selectors—all of the possible explanations that might account for the way reality at level 0 turns out. These include Simplicity, Goodness, Causal Orderliness, and Fullness, as well as the No Selector possibility—the possibility that there is no explanation at all.

At level 2, the meta-explanatory level, you have all the plausible meta-Selectors—all of the possible explanations that might account for which Selector prevails at level 1. These include—again—Simplicity, Goodness, Causal Orderliness, and Fullness, as well as the No Meta-Selector possibility.

Now let’s consider some cases.

First, suppose that no Selector explains why reality takes the form it does, and that there is no further explanation for why there is no Selector. Then it is a brute fact that reality takes the form A. But this violates Sufficient Reason. Dead end.

Next, suppose that one of the Selectors at level 1 does explain why reality takes form A. Call this Selector S. Then either there is an explanation for why