Whenever you see a philosophical text talking about nothing, it's sure to be quite important. Although the topic would seem rather void of any content, it is at least full of all sorts of ambiguities. Kant himself noted that there are at least four things that ”nothing” or Nichts could mean, although understanding these meanings requires understanding lot of Kantian philosophy. Here I am interested of a bit simpler ambiguity.
Consider first cases where we usually apply words like ”nothing”: ”there's nothing here”, ”no one is coming” and so forth. All of these examples indicate lack of some type entities – for instance, in the second case, a lack of persons. ”Nothing” seems thus remnant of what in modern set theory is known as empty set, a set with no members. In case of ”nothing”, as used in ordinary language, this lack is undoubtedly often just contextual: the first example can be used in a room full of socks, if it is shoes we are looking for.
Now, just as extension and intension in general have often been conflated, one tends to find confusion between ”nothing” in the sense given above (lack of entities) and concept having such ”nothing” as its extension. Thus, one might find such sentences as ”gold mountain is nothing”, when what is meant is that there are no golden mountains. This is then the first ambiguity involved with nothingness.
Wolff's notion of nothing might at first sight appear to correspond with the first of the senses indicated above – or at least Wolff notes that he uses term ”nothing” as corresponding with the arithmetical notion of nullity. Yet, the very definition of nothing Wolff gives points to another direction. Nothing, says Wolff, is such that corresponds to no notion – or as he later admits, it corresponds only to a deceptive notion. Furthermore, Wolff explicates that it is the principle of contradiction that explains when a notion is deceptive – that is, contradiction makes a notion a deceptive and refers only to nothing.
What we have here is then yet another common notion of ”nothing”: lack of possibility or impossibility. And just like with the very first notion of ”nothing”, there is also the possibility to confuse lack of possibility with a concept referring to such impossibility – we can find sentences like ”round square is nothing”, when all that is meant is that there cannot be any round squares. But what is more interesting is the relation of ”nothing” as lack of possibility to ”nothing” as lack of entities: we could describe the former ”nothing” as a lack of possible entities and the latter as a lack of actual entities. When Wolff then defines ”something” as a contradictory of ”nothing”, he must be referring to a presence of possible entities – or to concepts referring to such entities.
Now, one might wonder, what has all this to do with the principle of sufficient reason? Well, Wolff's infamous proof of the principle depends very much on that ambiguous notion. Let us presume an existing thing A without any reasons, Wolff begins. Then there is a ”nothingness” of these reasons, but such nothingness cannot produce anything, which contradicts the existence of A.
This rather curious argument suffers clearly from the ambiguity of the notion of ”nothing”. What it appears to be trying to deduce at first sight is that a lack of any reasons or grounds would fail to produce anything. Yet, as we have seen, Wolffian notion of nothingness does not refer to such lack of actual entities, but to a lack of possible entities. The starting point of the indirect proof is then the assumption that thing A couldn't have any reasons, that is, that its generation would be inexplicable impossibility. This clearly would contradict the very existence of A, which would indeed have to be possible, thus leading to the sought for conclusion or the denial of this nothingness.
Wolff's argument can then be maintained, but then its conclusion comes out as rather trivial. Wolff has shown that without any possibility of generating something, this something could not be, or in other words, that if something exists, there must be some possible way it has come into existence. It is then not necessary that this possible generation process would have been a deterministic causal link necessitating it, but it merely should have been a possible series of events leading to the existence of the particular thing. On the other hand, this fits well with Wolff's wish to account for non-causal chains of grounding in human action. Motives need not determine our actions, but they just need to open up a possible path for them – it might still be down to our choice, which path is taken.
What is more difficult to reconcile with this weak reading of the principle of sufficient reason is Wolff's second argument for the principle. Supposedly one could distinguish reality from dreams only through the principle of sufficient reason: while the former follows the principle, in the latter there happen all sorts of changes just willy-nilly or according to the whimsy of the dreamer. If the principle would be taken in the weaker sense, then there would be no contradiction between it and dreams, because even the most absurd dream sequences still are possible sequences.
Now, although the dream argument appears to speak for a stronger sense of the principle, it is not impossible to make it agree with the weaker sense also. Wolff might not be thinking of dreams contradicting the principle itself, but a conjunction of the principle with relevant physical laws. Thus, while e.g. sequence of me flying above the clouds would not be impossible as such, it would be impossible given the physical laws preventing such flight. This reading would actually make more sense, because when Wolff does say that the principle of sufficient reason is derivable from the principle of contradiction, anything contradicting principle of sufficient reason would be contradictory and impossible – which appears rather confusing, when we evidently can experience dream sequences.
This conclusion appears rather interesting, because early on it was the dream argument that was emphasised by the followers of Wolff. It seems plausible that this argument was chosen over the official proof of Wolff himself, because it was easier to reconcile with the stronger version of the principle of sufficient reason. In effect, the dream argument then gives a criterion for recognising reality: it is the lawlike nature of the reality that distinguishes it from dreams. One might even find such emphasis on lawlikeness in Kant's description of experience as regulated by the category of causality. If the weaker reading of the principle is correct in case of Wolff, his description of reality is far more modest: it is not the lawlikeness as such that distinguishes reality from dreams, but the fact that reality follows laws not followed by dreams.
So much for sufficient reasons, next time I'll look at essences.