Michael Della Rocca, in his paper PSR, defines the Principle of Sufficient Reason, the PSR, as the principle by which each fact has an explanation (1). For every object or state of affairs there can be given a reason for its existence. Della Rocca argues that the PSR is widely rejected by philosophers because it has failed to be adequately argued for and that there has been relentless attacks on the PSR over the last 270 years (1-2). Not only has there been relentless attacks on the PSR, but philosophers such as David Hume and Immanuel Kant have even constructed entire philosophical systems around the assumption that the PSR is false. To make matters worse, according to Della Rocca, there appears to be adequate reasons to give up on the PSR given evidence from contemporary physics (2). Despite acknowledging reasons to give up on the PSR, Della Rocca continues. Before giving his argument for the PSR, Della Rocca gives a few cases of so-called explicability arguments. An explicability argument is, for Della Rocca, “such an argument, [where] a certain state of affairs is said not to obtain simply because its obtaining would be inexplicable, a so-called brute fact” (2). The first example Della Rocca uses is an example from Gottfried Leibniz: “[Archimedes] takes it for granted that if there is a balance in which everything is alike on both sides, and if equal weights are hung on the two ends of that balance, the whole will be at rest. That is because no reason can be given why one side should weigh down rather than the other” (321). Leibniz does not consider the possibility of this fact being inexplicable, which would be a perfectly plausible inference. The point of this example is to illuminate the legitimacy of explicability arguments, in at least some cases. If Della Rocca can get the reader to accept explicability arguments generally, then he has forced the reader to accept the PSR itself. This is because, as Della Rocca defined earlier, the PSR is the claim that each fact has an explanation, the rejection of inexplicability generally. To accept the PSR, under the definition given here, is to reject brute facts.
It seems plausible that the above example may point to an instance in which an explicability argument works, but it seems that one can accept the above argument without being committed to explicability arguments generally. Della Rocca offers a second example of a seemingly plausible explicability argument, he calls these brute dispositions (2). Della Rocca offers his second example as follows:
“Imagine two objects that are in the same world and that are categorically exactly alike. They each have (qualitatively) the same molecular structure and have all the same categorical physical features. If one of these objects has the disposition to dissolve in water, could the other one fail to have that disposition? It would seem not: given their exact categorical similarity, nothing could ground this dispositional difference between the two objects, and so we reject the scenario in which there is such a difference” (3).
This is another instance in which it seems that an explicability argument is justified. Such an argument seems to work because there is no explanation as to why one object would dissolve and the qualitatively identical object fail to.
Once again, the reader still is not forced to accept the PSR. Della Rocca offers a number of other examples of explicability arguments, but they are not necessary to the understanding of the argument as a whole. The goal of Della Rocca’s examples are to show instances in which explicability arguments are successful. The point is that philosophers often want to appeal to explicability arguments, whether it is in regards to consciousness, rejecting Aristotelian explanations, defending induction, causation, modality, and so on. All of these phenomena seem to involve appealing to explicability arguments. All of the instances in which explicability arguments are successful not only give intuitive support for the PSR, but these arguments also make it more difficult to draw a non-arbitrary line between when explicability arguments are acceptable and when they are not.
The final case that Della Rocca considers is that of existence. While the previous cases do not commit one to the full-blown PSR, the case of existence does entail the PSR. Della Rocca believes there is no non-question begging, non-arbitrary, way of rejecting the PSR in the case of existence. In this way, explicability in the case of existence amounts to an argument for the PSR. Just as the previous examples may or may not have asked for explicability arguments for various phenomena the same can be done for existence itself. Della Rocca best illuminates the importance of explicability in the case of existence as follows:
“…the explicability argument in the case of existence differs from the previous ones in one crucial respect: while the other explicability arguments do not by themselves commit one to the full-blown PSR, the explicability argument concerning existence does, for to insist that there be an explanation for the existence of each existing thing is simply to insist on the PSR itself, as I stated it at the outset of this paper. So the explicability argument concerning existence, unlike the other explicability arguments, is an argument for the PSR itself, and it is our willingness to accept explicability arguments in other, similar cases that puts pressure on us to accept the explicability argument in the case of existence, i.e., puts pressure on us to accept the PSR itself” (6-7).
The above passage is Della Rocca’s major argument for the PSR. Appealing to an explicability argument in the case of existence is to assert the PSR itself because the PSR is the claim that everything has an explanation. That is, for each thing that exists there can be given a reason for its existence. Given the above argument, Della Rocca considers three options that the denier of the PSR could take:
1. One can say that some of the explicability arguments are legitimate and some—in particular, the explicability argument concerning existence—are not.
2. One can say that none of the explicability arguments is legitimate.
3. One can say that all of the explicability arguments, including the explicability argument concerning existence, are legitimate (7).
None of the above options end up being appealing to the denier of the PSR. The denier cannot take option three because to accept explicability arguments, including the case of existence, is to accept the PSR itself. Della Rocca offers a sophisticated response to the second option, but the response essentially comes down to the fact that it seems like the entire practice of philosophical and scientific inquiry depends on explicability arguments, or the denial of brute facts and the demanding of explanations. The examples of explicability arguments in this paper are instances in which philosophers want to make appeals to explicability arguments. Many philosophical arguments appear to be explanations. There is nothing wrong, logically, with taking the second option, but it prevents one from appealing to explicability arguments in the cases of Archimedes’ balance, consciousness, personal identity, mechanistic explanation, induction, causation, modality, and so on. The second option does not come without considerable cost.
The first option is most likely the most appealing option to the denier of the PSR. If one wants to draw a line between legitimate and illegitimate explicability arguments, then, for Della Rocca, one must draw principled and non-arbitrary line (7). If the denier of the PSR attempts to draw an arbitrary line, then the denier is begging the question against the PSR because to appeal to an arbitrary line is to appeal to inexplicability and that is to assume the PSR is false (8).
Leibniz, Gottfried Wilhelm, Roger Ariew, and Daniel Garber. Philosophical Essays. Indianapolis: Hackett Pub., 1989. Print.
Rocca, Michael Della. “PSR.” Philosophers’ Imprint, July 2010. Web. 7 Mar. 2016.