The Aptness of the Ontological Argument
There is a kind of abductive argument from aptness, or fittingness, that some philosophers and theologians have employed in the past. For example, Bl. Duns Scotus develops an argument for the Immaculate Conception from its fittingness.
What is aptness? It seems to be an explanatory feature like parsimony, or conservativeness. It is something that, were we to discover its truth, we would not be surprised, given what we presently understand of the topic. Moreover, in contemplating the aptness of a hypothesis, one has a sense that such a truth, though unsurprising, is nonetheless illuminating.
Now, the aptness of a hypothesis, insofar as it seems to be an abductive explanatory feature, does not appear to be the intuition of merely an analytical or tautological truth, even, say, within counterfactual contemplation. For example, I wouldn’t really say that it is apt that, should there be a sound proof that the Goldbach conjecture be true, that the proof would be mathematical in nature. For, to say that is just really to state the implicit tautology that if there is a sound mathematical proof for x, then there is a sound mathematical proof for x, and tautologies like that are not, in any way, illuminating, which is at least part of what we mean by “apt.”
I have explained aptness through a kind of subjunctive conditional, i.e. ‘if x were true of y, it would be apt that x is true of y.’ That alone might be some reason to think it is probable that x is true of y. However, if there is also evidence that is consistent with the claim of aptness, it would be reasonable, all the more, to increase the likelihood that x is true of y.
So, what of the ontological argument? Or more precisely, what of a priori arguments that purport to establish the existence of God, i.e. a maximal great, supreme, or perfect being. It seems apt that if any concrete object should be established solely through a priori considerations, then God would be a candidate. Nay, given the supposed chasm between creature and creator, it is apt that, among concreta, God alone should be proved to exist solely by a priori considerations.
Put in terms of our formula, we could say, “If God alone, among concreta , could be proved to exist solely by a priori considerations, then it would be apt that God alone, among concreta, can be proved to exist solely by a priori considerations.” And this might be some reason to think a version of the ontological argument is plausible. Now consider the evidence in support of the hypothesis — i.e. the lack of ontological arguments for any other concrete objects (leaving aside the possibility of ontological arguments for objects in an abstract realm), and the plethora of candidate ontological arguments for a supreme being. These facts of philosophical history, that ontological arguments seem only to be suited to establish the existence of God, I would contend, a good abductive reason to think it is plausible that there be a sound ontological argument.
Perhaps, though, you are not moved that the aptness of the ontological argument should makes us think that such an argument is probably sound. Aptness may still be sufficient to establish the soundness of an ontological argument. How so? Well, it seems to me that if we should think that a feature increases the probability of a hypothesis this entails not that it is broadly logically possible, but that we should think it is broadly logically possible. That is, if our considered judgment is that we think there is evidence for a hypothesis, which increases the likelihood of that hypothesis, then we are committed to thinking the prior probability of the hypothesis is not 0. This does not establish that a sound ontological argument is, in fact, possible, but that one who is committed to their being evidence for a sound ontological argument is, in fact, committed to the real possibility for it. But then, if one thinks such an argument is possible, one should also think such an argument, in fact, exists.
We might reason as follows:
P1. If one should think there is good evidence to support the claim that it is apt that God alone, among concreta, can be proved to exist solely by a priori considerations, then one should think that the probability of the hypothesis ‘God alone, among concreta, can be proved to exist solely by a priori considerations’ has increased.
P2. If one should think that the probability of the hypothesis ‘God alone, among concreta, can be proved to exist solely by a priori considerations’ has increased, then one should think that it is broadly logically possible that God alone, among concreta, can be proved exist solely by a priori considerations.
P3. If one should think that it is broadly logical possible that God alone, among concreta, can be proved exist solely by a priori considerations, then one should think that, in fact, God alone, among concreta, can be proved exist solely by a priori considerations.
P4. One should think there is good evidence to support the claim that it is apt that God’s existence alone, among concreta, can be proved to exist solely by a priori considerations.
C. So, one should think that, in fact, God alone, among concreta, can be proved to exist solely by a priori considerations.
Defense of the premises:
In defense of P1, one can say that to have good evidence to support the explanation for a hypothesis just is to make that hypothesis more likely than it otherwise would be. We can simply stipulate that this is what we mean by good evidence, i.e. it is sufficient to imply the plausibility of the hypothesis in question.
In defense of P2, we are not actually, as some might fear, shifting from epistemic possibility to broad logical possibility, strictly speaking. We are couching this implication within what one should think, given one’s epistemic duties. Whether or not something is, in fact, broadly logically possible, if one thinks something is not, a priori impossible, one cannot, rationally, at the same time remain agnostic to its broad logical possibility. To think that a hypothesis might become more likely, given the evidence, entails that one, thinking appropriately, also thinks the hypothesis is inherently possible. Otherwise, no evidence would improve the probability. Hence, the rational person who thinks there is evidence that is suggestive some sound ontological argument, that person ought to think that such an argument is really possible, in a robust sense.
For P3, I would simply note that, given the fact that a priori ontological arguments derive modally necessary conclusions, from a priori necessary truths. Such an argument would, in effect, be sound across possible worlds. Indeed, the very counterfactual I have contemplated in this post “If God alone, among concreta , can be proved to exist solely by a priori considerations, then it would be apt that God alone, among concreta, can be proved to exist solely by a priori considerations” could be assessed as true, like other subjunctive conditionals, in terms of possible worlds, e.g. in the nearest possible world where God alone, among concreta, can be proved to exist solely by a priori considerations, it is explanatorily fitting and apt that such is the case, and that is just to affirm P3.
Finally, P4 is based on the above considerations. I think it is basically intuitive that it should be apt that the ontological argument should work only for God, and for no other concrete object. The fact that there have been dozens of formulations of the ontological argument that are, at the very least, plausibly sound, and no ontological argument for any other concrete thing only goes to support this aptness, and so make this aptness not only likely, but provide abductive support for one to embrace the possibility of some sound ontological argument for God. Now, one might say that there are evidential matters to consider, but I am not compelled to think so. If Plantinga’s own version of the argument is correct, then the possibility of a maximally great being is at least reasonable to believe on its own. Moreover, there appears to be substantive responses to arguments for the incoherence of theism, and I take that to be the primary counter-evidence to the ontological argument. Given that, I think the aptness of the ontological argument, and the evidential support for it, is sufficient to make it plausible that there is sound ontological argument.
From this, it follows that we should think God exists.