PSR, PvI, and the Multiverse
According to a strong and unrestricted version of the principle of sufficient reason, everything that exists or occurs has a sufficient reason for its existence or occurrence, where sufficient reasons are taken to entail or necessitate the existence or occurrence of the entity in question. For our purposes, call this version PSR.
Peter van Inwagen famously argued that PSR is implausible, as it entails that everything exists or occurs of metaphysical necessity, and that this is absurd (since many things seem to be contingent and not necessary). Call this the PvI objection. Now people tend to react to the PvI objection in one of three ways:
(i) Hold on to PSR, while accepting that it entails everything exists or occurs of metaphysical necessity.
(ii) Restrict PSR so as to make conceptual space for things to occur contingently.
(iii) Reject PSR in order to make conceptual space for things to occur contingently.
However, it seems to me that there is another option:
(iv) Hold on to PSR and its implication that everything exists or occurs of metaphysical necessity, but deny that it entails that everything exists in our universe exists or occurs of necessity in all universes.
To motivate this option, note that the PvI objection gets most of its bite by assuming that
1. Our universe is the only universe that exists at the actual world.For then it seems to follow from (1) and the PvI objection that
2. Whatever exists or occurs in our universe at the actual world exists or occurs in all possible universes at all possible worlds.However, if it's possible that there is a multiverse comprising an infinite number of universes (where these are sufficiently diverse so as to capture our modal intuitions about the space of metaphysical possibilities), then this inference doesn't go through.
Option (iv) exploits the epistemic possibility of a multiverse of the sort sketched above to block the inference from (1) and the PvI objection to (2). Those who take this option grant that PSR entails that everything exists or occurs of metaphysical necessity, in the sense that the multiverse at the actual world exists at all possible worlds. However, they deny that all that exists or occurs in our tiny corner of the multiverse exists or occurs at all other universes within the multiverse. In this way, they deflate the epistemic significance of the intuition of contingency that gives the PvI objection its bite. By choosing option (iv), then, one can have one's explanatory cake and eat it, too.
I'm not saying that option (iv) doesn't raise questions of its own. (E.g., does it commit one to Lewisian modal realism and/or counterpart theory? Etc., etc.). All I'm saying is that (iv) is an option that's no worse off than the others, and that it's not clear that it fares worse than PvI's option in terms of a theoretical cost-benefit analysis between the respective views. At a minimum, it's an option that deserves more consideration than it has hitherto received.
Metaphysically Necessary Beings, Factually Necessary Beings, and Two Kinds of Brute Facts
I've argued for the live epistemic possibility that matter/energy (or, if matter/energy isn't fundamental, the stuff of which matter/energy is ultimately composed) is factually necessary. That is, it's a live epistemic possibility that while there might be possible worlds at which matter/energy does not exist, it's eternal, uncaused, existentially independent, and de facto indestructible at the actual world. I've also argued that factually necessary matter/energy satisfies a weaker version of PSR:
(PSRfn): Every existing thing has an explanation of its existence, either in terms of the factual necessity of its own nature or in terms of an external cause.
Finally, I've attempted to motivate this proposal and answer a number of objections to it on various occasions. Here, however, I'd like to set aside these points and defend PSRfn by means of a tu quoque argument of sorts. Here's a thumbnail sketch of the argument: A number of proponents of the principle of sufficient reason (PSR) have accepted a revised version that allows for brute facts of certain sorts, on the grounds that unrestricted versions of PSR lead to absurdities, or conflict with other things we have reason to accept. And because of this, they reason, such revisions, and the resultant acceptance of certain sorts of brute facts, are acceptable. But (I argue) if such a basis for revising and restricting PSR (and thereby allowing for certain sorts of brute facts) is acceptable, then by the same token, so is the basis for further revising PSR to PSRfn, and, consequently, granting the acceptability of the brute existence of a factually necessary being.
Of course the key move in the argument is following recent proponents of PSR in accepting a distinction between between objectionably vs. unobjectionably brute facts. Here's a quick sketch and illustration of the distinction:
Of course the key move in the argument is following recent proponents of PSR in accepting a distinction between between objectionably vs. unobjectionably brute facts. Here's a quick sketch and illustration of the distinction:
1. Objectionable: there is no explanation of a contingent fact, and there is no good reason to accept this.
-Example: an iPhone pops into existence without any cause whatsoever.
-Example: an iPhone is produced without preexisting materials.
2. Unobjectionable: there is no sufficient reason for a contingent fact, but there is a good independent reason to accept this.
(a) Assuming that x has a sufficient reason for its existence or occurrence leads to an apparent absurdity.
-Example: Such an assumption entails that everything exists or obtains of absolute
necessity, that we lack free will, that quantum indeterminacy isn't real, etc.
(b) Assuming that x has a sufficient reason for its existence or occurrence conflicts with other things we have reason to accept.
-Example: Such an assumption conflicts with (say) a priori and/or a posteriori evidence that no being is metaphysically necessary.
Here's my claim: Positing that there is no sufficient reason for why an independent being exists beyond the factual necessity of its own nature, and is thus a brute fact, is of an unobjectionable sort. In particular, it's a brute fact of type 2(b), since assuming the contrary conflicts with something else that we have reason to believe, viz., that no being is metaphysically necessary. Here are three reasons one might offer for thinking that no being is metaphysically necessary:
(i) Modal evidence: We have modal intuitions that for any being, there are worlds at which it doesn’t exist.
(ii) Abductive evidence: our extensive experience of an extremely wide variety of concrete objects is such that we find them all to be contingent. What explains this? The simplest, most conservative explanation of the data with the widest explanatory scope is the hypothesis that all concrete objects are contingent beings.
(iii) Origin essentialism: Widely shared intuitions support the Kripkean thesis that objects have their origins of metaphysical necessity: for any world W and objects x, y, and z, if x was produced by y and z at W, then x was produced by y and z at every other world W' at which x exists. So by implication, if an eternal universe lacks an origin at the actual world, then it lacks an origin at every world. And if that's right, then it's metaphysically impossible for such a universe to have a further explanation for its existence.
For at least these reasons, then, the existence of a factually necessary universe is unobjectionably brute, since assuming the contrary conflicts with other things we have reason to accept.
(i) Modal evidence: We have modal intuitions that for any being, there are worlds at which it doesn’t exist.
(ii) Abductive evidence: our extensive experience of an extremely wide variety of concrete objects is such that we find them all to be contingent. What explains this? The simplest, most conservative explanation of the data with the widest explanatory scope is the hypothesis that all concrete objects are contingent beings.
(iii) Origin essentialism: Widely shared intuitions support the Kripkean thesis that objects have their origins of metaphysical necessity: for any world W and objects x, y, and z, if x was produced by y and z at W, then x was produced by y and z at every other world W' at which x exists. So by implication, if an eternal universe lacks an origin at the actual world, then it lacks an origin at every world. And if that's right, then it's metaphysically impossible for such a universe to have a further explanation for its existence.
For at least these reasons, then, the existence of a factually necessary universe is unobjectionably brute, since assuming the contrary conflicts with other things we have reason to accept.
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