We’ve already learned here and here some of the main steps in the Shaykh al-Rai’s’ Burhan al-Siddiqin. Here I want to take up a certain criticism of it by the Ash’arite mutakkalim and Sufi al-Ghazali (d.1111) as developed by H. Davidson in his Proofs for Eternity, pp.304-7. The objection is specifically directed at the part of the Shaykh’s argument which concerns the relations involved between an aggregate of mumkinat, its individuals taken individually, and their cause. I will first state al-Ghazali’s and Davidson’s objections; then I will try and respond to them on Ibn Sina’s behalf.
Al-Ghazali’s and Davidson’s criticisms
In the Tahafut al-Falasifah, at 4.18.19-26, al-Ghazali objects to the Shaykh’s proof as follows:
The expressions “the possible” and “the necessary” are vague expressions, unless by “the necessary” is intended that whose existence has no cause and by “the possible” that whose existence has a cause. […]. We will thus say: “Each one [of the causes] is possible in the sense that it has a cause additional to itself, and the whole is not possible [but necessary] in the sense that it does not have a cause additional to itself, extraneous to it. […].
Elaborating on the above, Davidson’s maintains that Ibn Sina failed to consider another possible disjunct, which he takes al-Ghazali to have hinted at here, when Ibn Sina divided the cause of the totality (jumla) of possible existents into either (1) one of the members/components of the totality or (2) something altogether external to the totality. According to Davidson, there’s a third possibility here i.e., “the thesis that the totality is maintained in existence not by a single component but by all the components together.” In other words, all the members of the totality of possible existents as a whole, and not any member taken individually, are the cause of the existence of the totality. As such, the totality would be “possibly existent by virtue of itself, necessarily existent by virtue of its [internal] components.” Davidson then says that if someone should object, on behalf of the Shaykh, that ‘the new alternative would amount to a case of self-causation’ (i.e., because since if (a) the cause of the whole is first of all the cause of the components making up the whole and if (b) each component is a part of the cause of the totality, then it would follow that (c) each component would be a part of the cause of the existence of itself) he would respond by demanding an argument, which he thinks the Shaykh lacks, that would show that a “possible existent being cannot be even part of the cause of the existence of itself.” A somewhat helpful, but ultimately misleading, analogy Davidson employs to get his point across here is that of a circular arch in which each stone maintains the whole in position. By maintaining the whole in position, he says, each stone is a part of the cause that is maintaining itself in position.
Ibn Sina’s response
Admittedly, the version of the Shaykh’s proof which Davidson (though not al-Ghazali) criticizes here – the one contained in his Kitab al-Najat – does not explicitly eliminate the third possibility which was suggested above. However, it doesn’t follow that Ibn Sina was therefore not aware of it; in fact, he explicitly cites, and subsequently rejects, it as an option in the version of the proof contained in his Kitab al-Isharat. Let me now turn to that text.
In Namat IV of the Kitab al-Isharat, the Shaykh, after having established, in fusul 10 and 11, that the existence of what is mumkin bi’l-dhat is from other than it and that this is so even if such mumkinat should regress infinitely, in fasl 12 writes the following:
Commentary. Every aggregate [jumla] whose individuals are caused, requires a cause external to its individuals. [a] This is because either it does not need a cause at all, […]. [b] Or else, it needs a cause which is the individuals all together, so it would be caused by itself, for this ‘aggregate’ and ‘all [i.e., its individuals]’ are one and the same. As for ‘all’ in the sense of each individual – the aggregate is not necessitated by it. [c] Or else, it needs a cause which is one of the individuals, […]. [d] Or else, it requires a cause external to all its individuals. […].
The fully stated disjunct, i.e., [b], is the focus of attention here. In my judgment it amounts to Davidson’s third option above which he accused Ibn Sina of neglecting. Its refutation by the Shaykh is fairly, but subtly, straight-forward. The disjunct has it, as Davidson said, that the cause of the aggregate of the mumkinat is simply all the individuals of that aggregate taken together. But as Ibn Sina remarks, the problem with holding this is that it amounts to a concealed case of self-existentiation or causation, not in the sense in which it was stated above by Davidson, but in the sense that ‘the totality’ (of possible beings) and ‘all the components’ (of the totality) are coterminous! That is to say, the two terms just mean the same thing. The totality or aggregate of possible beings is nothing other than all of them considered together. Hence, Davidson’s third option here would reduce to the claim that ‘the totality exists through the totality’, which further reduces to the claim that ‘the totality is caused by the totality’. But, for reasons I will not get into here, self-causation, Davidson would agree, is absurd. Therefore, this part of Davidson’s objection, it seems to me, fails. As for the part of his objection which demands for an argument which shows that, in the aggregate of mumkinat, a “possible existent being cannot be even part of the cause of the existence of itself”, I believe the Shaykh’s statement “as for all in the sense of each individual, [etc]”, supplies it. The claim here is that the individuals taken together may cause the aggregate qua each individual member. The Shaykh’s answer – namely, that “the aggregate is not necessitated by [each individual member]” – means, I take it, that insofar as what is being explained is the aggregate of mumkinat, everything that falls within it (i.e., all its members) ipso facto has a cause. As such, none of its members would necessitate it; that is, qua individuals, they would only necessitate their immediate single effect, not the whole aggregate.
At another place in the same section, presumably in support of his third option above, Davidson says a “being can be necessary in itself even when existing by virtue of its parts.” This is a contradiction though. For a whole that is composed of parts, whether external or internal, causally depends on those parts. How then can such a being be necessary in itself? Otherwise, the entire series of contingents (as a whole) will not be different from a single contingent. For the latter is necessary through its cause just as much as the former; and is also just as much dependent on its cause as the former. But it is not necessary in itself! Again, Davidson says that “[Ibn Sina] does not explain exactly why possibly existent beings cannot add up to a being necessarily existent by virtue of itself.” I maintain, though, that Ibn Sina does in fact explain why this is the case. And the reason is not, as Davidson suggests, because the necessarily existent ‘can contain no components whatsoever’. The reason, I believe, goes deeper than that, namely, because contingency or possibility cannot by itself ever give rise to necessity. That is, nothing that is possible in itself, whether finite or infinite, necessitates its own existence.