1 Introduction
It is customary to begin with praise for the author’s book.Footnote
1
And there is much to praise! Nick Stang has written a wonderful book that illuminates many aspects of Kant’s metaphysics, including, but not limited to, his modal metaphysics. It is carefully written, the arguments are tightly constructed, it is historically sensitive and it addresses a centrally important but underexplored aspect of Kant’s philosophy. But even though it is customary to begin with praise, I will not do that, since custom yields merely subjective necessity. Otherwise, I would highly recommend this book to the readers of this journal, and, more generally, to philosophers interested in either metaphysics or the history of philosophy. This book is terrific.
In what follows, I focus on two things. First, in section 2, I discuss a concern about Stang’s interpretation of Descartes. Stang discusses a view that he calls ontotheism and attributes versions of it to several philosophers, including Descartes. The ontotheist is a proponent of the ontological argument. Stang’s Kant takes the ontotheist to be committed to possibilism, the doctrine that there are, or at least could be, non-existent individuals.Footnote
2
But, in my view, his Kant does not discuss the best version of Descartes’ ontological argument. Specifically, I do not think that Descartes’ most promising version of the ontological argument commits him to possibilism.
However, if I am right, this does not show that Stang got Kant wrong. I think that he interprets Kant correctly, but that Kant’s argument is ineffective against Descartes. At the very least though, I’ll get this version of the ontological argument on the table and we can see who, if anyone, misunderstands anyone else.
The second thing I focus on is Stang’s discussions of real possibility. He distinguishes several kinds of real possibility. How do the various kinds of real possibility relate to one another? How do they relate to what contemporary metaphysicians call metaphysical possibility? And how do they relate to adjacent phenomena such as ground and real essence? In section 3, I raise worries about Stang’s formulations of various doctrines of real possibility. In section 4, I preliminarily explore how real essence and ground are connected with the various kinds of real necessity Stang’s Kant recognizes.
2 Descartes and Ontotheism
Ontotheism is the view that God’s essence explains God’s necessary existence. According to Stang, proponents of the ontological argument are ontotheists. And on his interpretation of Kant, Kant thinks that ontotheism entails possibilism. Stang understands possibilism as the view that there are some things that do not exist but could exist. Given possibilism, existence is a determination – it is a feature that some but not all things have. However, Kant argues that existence is not a determination, and so possibilism is false, and hence ontotheism is false.
Although it is controversial whether Descartes was a possibilist, I suspect he probably was not.Footnote
3
More importantly, at least one of his versions of the ontological argument can be formulated even given that possibilism is false.
On the interpretation I favour, the key component of Descartes’ ontological argument is that essence precedes existence.Footnote
4
But it is not part of Descartes’ argument that there are things that merely possibly exist, although he does accept that essences are always possibly exemplified. Here is how I construe the argument. I have a clear and distinct idea of God. Having a clear and distinct idea of x just is grasping the essence of x. But any essentialist statement is necessarily true, independently of whether the possessor of that essence exists; this is the view that essence precedes existence. Since I grasp the essence of God, there is a necessary truth to be grasped about God’s essence. The complete essence of God is that God exists.Footnote
5
Conclusion: so, necessarily, God exists.
On this way of understanding Descartes, claims of the form it is essential to x that Fx can be true even in possible situations in which x does not exist. If we want to regiment the logic of Cartesian essentialist claims, we could use a free logic. (Briefly and roughly, in a free logic, from the fact that Fb, it does not logically follow that something is F.) Stang briefly notes that a version of ontotheism employing a free logic is possible, although not in the context of regimenting Descartes’ views (p. 32, n. 89). He has some things to say about the use of free logic in this sort of context in an online supplement to the book, but I am honestly not sure I understand his response there. We will come back to this momentarily.
In what follows, I will use ‘ □
x
’ as an abbreviation of ‘it of the essence of x that’. The motivation for using a free logic in this context is that it allows us to accept every instance of ‘□
x
Fx entails □Fx’ without being committed either to the necessary existence of everything, or to possible things that could exist but do not exist. In general, essentialist truths imply modal truths (and are themselves necessarily true) even though the objects of those essential truths need not necessarily exist. However, when ‘F’ stands for existence, we have an essentialist claim which if true implies the necessary existence of the object of that essentialist claim. This is true even if existence is defined in terms of quantification, that is, even if what it is for x to exist is for x to be identical with something.
In short, on my view, it is the claim that essence precedes existence rather than possibilism per se that does the work in Descartes’ strongest version of the ontological argument. Descartes is not committed to possibilism qua defender of the ontological argument.
As mentioned a few paragraphs back, Stang discusses the use of free logic to defend ontotheism in an online supplement to the book, in which he writes the following:
What then explains the necessary non-emptiness of the name of God? The natural ontotheist view is that ‘God’ is necessarily non-empty because it is essentially the name of God (where the name is individuated semantically rather than orthographically), and God exists necessarily (in virtue of his essence), so ‘God’ necessarily names God and hence is necessarily non-empty. Consequently, I think the ontotheist equipped with a free logic is still forced back upon the basic ontotheist metaphysics (God’s essential existence) to explain the necessary non-emptiness of the name ‘God.’Footnote
6
Let me grant everything in the quoted passage above. I am confused by what comes next. Stang writes:
But if this is correct the ontotheist must give an underlying metaphysics without appealing to the emptiness or non-emptiness of the name of God – because that underlying metaphysics is meant to explain the modal status of names (why some are contingently non-empty and others are necessarily so). Consequently, I think the ontotheist is forced into the same metaphysical conclusions I argue for in the text of the book.
In this context, the relevant metaphysical conclusion is that the ontotheist is committed to possibilism; this is the relevant alleged conclusion, since by ruling out possibilism via the claim that existence is not a determination, ontotheism would also be refuted. But I do not see an explanation of how the ontotheist who employs free logic is committed to possibilism – and hence how Descartes thus regimented would be either. I am hoping Stang can say more here.
Remember why this matters: it is crucial to Kant’s criticism of the ontological argument that existence is not a determination. On the version of Descartes’ ontological argument described earlier, whether or not existence is a determination is irrelevant to the success or failure of that argument.
3 Real Possibility
Let us turn now to Stang’s discussion of real possibility. Kant distinguishes real possibility from logical possibility. A concept is logically possible if and only if the judgement that it has an instance is non-contradictory. But not being contradictory is not sufficient for being really possible.
Contemporary metaphysicians by and large grant this Kantian insight, and accordingly distinguish between metaphysical possibility (or genuine possibility) and logical possibility (or logical consistency). By and large, contemporary metaphysicians understand metaphysical possibility as the widest kind of genuine possibility, and are happy to recognize other kinds of genuine possibility. Something might be such that I can make it actual – and so this something is possible in some more restricted way but is nonetheless metaphysically possible as well. Similarly, to be nomologically possible is to be genuinely compatible with the laws of nature.
On the contemporary way of thinking, each kind of genuine possibility is a restriction on metaphysical possibility, which is the most general kind of genuine possibility. Let K-possibility be a kind of genuine possibility: P is K-possible just in case P is metaphysically possible and X, where the X indicates the additional condition P must meet in order to not be merely metaphysically possible but also K-possible. On the contemporary way of thinking, these different kinds of genuine possibility are kinds of metaphysical possibility in the way that the kinds lion and frog are kinds of animal. Of course there are different kinds of animals – but animal is nonetheless a unitary genus. There are a plurality of animals, but monism about being an animal is nonetheless true. The contemporary view is a kind of monism about metaphysical possibility.
Let us return to Stang’s Kant. Stang tells us that Critical Kant’s term for metaphysical possibility is real possibility. On the Critical Kant’s behalf, Stang also distinguishes various kinds of real possibility. However, unlike the contemporary metaphysician, Stang’s Kant appears to be committed to a kind of pluralism about metaphysical possibility itself. Although Stang is not explicit about this in his book, it seems that his Kant is committed to the claim that there is no such thing as the most general kind of genuine possibility of which each kind of real possibility is a species. There is no overarching unique kind of metaphysical possibility. On such a view, there might be kinds of real possibility K1 and K2 such that P is K1-possibile but K2-impossible, and there is no further fact about whether P is absolutely possible or not. Here is an analogy for understanding Stang’s Kant: just as there is no common genus of which alethic possibility and deontic possibility are species, there is no common genus of which the various kinds of real possibility are species. That said, there might be several formal or substantive features that various kinds of possibility have in common with each other, and these common features might explain why it is reasonable to call each of them ‘real possibility’.
As just mentioned, I think Stang’s Kant is committed to a deep kind of pluralism about metaphysical possibility – although I think much of what Stang says in the book is superficially compatible with monism about metaphysical possibility. Here are some passages to consider.
The various different kinds of real possibility he accepts are unified by a common scheme: real possibilities are grounded in an absolutely necessary first ground. For each kind of real possibility, there is a corresponding conception of an absolutely necessary ground: space (formal possibility), the laws of nature (empirical possibility), real essences (nomic possibility), and God (noumenal possibility). Kant retains his pre-Critical conception of real possibility, generalizes from it to a set of general conditions on any concept of real possibility whatsoever, and then instantiates it at the level of various particular kinds of possibility. (p. 8)
In the Critical philosophy Kant deploys several different kinds of real possibility without explicitly distinguishing them; in this chapter I will distinguish three of them and, in the next chapter, a fourth. What makes all of these different kinds of possibility kinds of real possibility is that they obey Non-Logicality and Groundedness (with modifications to be noted below). (p. 198)
First, it [real possibility] is systematically unified because all of these different kinds of real possibility exhibit a common scheme in virtue of which they are kinds of real possibility. (p. 260)
None of these passages settle by themselves whether to understand Stang’s Kant as a monist or a pluralist about metaphysical possibility. However, as we will see in a moment, there is a good reason to ascribe pluralism to his Kant. That said, Stang (p. 268) does say that the unschematized category of possibility corresponds to the most general kind of real possibility. But this claim is more consonant with monism about metaphysical possibility. Moreover, as suggested by the quote above from p. 198, Critical Kant does not explicitly distinguish various kinds of real possibility – and this fact might engender worries about whether Kant is a pluralist about metaphysical possibility. (If he is a pluralist, why does he not explicitly distinguish various kinds of metaphysical possibility?)
It will be helpful in what follows to quote Stang’s definitions of formal possibility and formal necessity:
(Formal necessity) It is formally necessary that p if and only if the fact that p is wholly grounded in facts about the actual intuitional form (space and time) and conceptual form (categories) of experience. (p. 203)
(Formal possibility) It is formally possible that p if and only if it is not the case that facts about the actual intuitional form (space and time) and intellectual form (unity of apperception) wholly ground the fact that ¬p. (p. 205)
Note that, when discussing whether formal possibility is a kind of real possibility, Stang merely claims that it satisfies several necessary conditions for being a kind of real possibility, but he does not explicitly say that it satisfies any sufficient conditions for being a kind of real possibility.Footnote
7
This would be unproblematic if Stang’s Kant were a monist about metaphysical possibility, for then the sufficient condition for a proposition P to enjoy real possibility of kind K would simply be that P is metaphysically possible and satisfies the stated necessary condition on enjoying K-possibility. In general, a monist about metaphysical possibility has a straightforward criterion of real possibility: all kinds of real possibility entail absolute metaphysical possibility. To see this, consider again nomological possibility. That P is logically consistent with the laws of nature is necessary but not sufficient for P to be nomologically possible. But that P is metaphysically possible and consistent with the laws of nature is necessary and sufficient for P to be nomologically possible. (This is because, on the monist’s view, kinds of real possibility are species of one single genus.) But if Stang’s Kant is a pluralist about metaphysical modality, saying this is not an option. And in this case, if we want to grasp the different kinds of real possibility, we should be unsatisfied with mere necessary conditions that a kind of putative possibility must meet in order to be a kind of real possibility. In fairness to Stang, any kind of pluralist faces a similar question: if you think there are ways of being F, what makes a given G a way of being F? And perhaps, in general, the pluralist can say nothing more illuminating than that the various ways of being F are sufficiently analogous to each other to count as modes of the same overarching yet less specific property.Footnote
8
Relatedly, note that Stang defines the various forms of real possibility and necessity so that they obey analogues of the box/diamond interchange rules in modal logic. That is, for each kind of possibility K, it is K-possible that P if and only if it is not K-necessary that not-P. For example, as you can see in quoted material above, P is formally necessary if and only if not-P is not formally possible. It is plausible that every form of real possibility and its corresponding form of real necessity should obey a box/diamond interchange rule.
However, given how Stang formulates the various kinds of real possibility, strictly speaking, real possibilities need not have grounds for their possibility, but merely require a lack of grounds for their non-actuality. Note that, given the definition of formal possibility above, it is consistent with P’s being formally possible that there is no ground for P period, let alone a ground of the (absolute metaphysical) possibility of P. In general, for any absolutely ungrounded truth P and any kind of real possibility K discussed by Stang, it is K-possible that P. What these observations suggest is that Stang’s account of formal possibility does not capture the idea that formal possibility qua real possibility requires positive grounds for its possibility, not merely an absence of grounds against its actuality.
In general, it does not seem that there is a close connection between the lack of whole grounds for ~P and P’s enjoyment of a kind of real possibility. Consider fake possibility. Say that P is fakely possible if and only if it is not the case that facts about what Donald Trump believes wholly ground the fact that ~p. I assume many propositions are fakely possible. Moreover, fake possibility obeys non-logicality. The non-logicality constraint is that, for any P and kind of real possibility K, it is not a conceptual truth that if it is logically possible that P, then it is K-possible that P. And it is not a conceptual truth that if it is logically possible that P, then it is fakely possible that P. The groundedness constraint is that, if something is fakely possible, it is fakely possible in virtue of how some actual object is.Footnote
9
Fake possibility also meets the groundedness constraint – or at least, it obeys groundedness to exactly the same extent as the other kinds of real possibility as defined by Stang, since all kinds of real possibility satisfy this constraint by way of absence of grounds for falsity rather than presence of grounds for possibility. But I see little reason to think that fake possibility is a kind of real possibility. Sad!
If we were monists about genuine possibility, we could easily deny that fake possibility is a kind of real possibility. But it is less clear how to rule out fake possibility given pluralism about genuine possibility. Perhaps, as noted earlier, the best thing to say is simply that the various kinds of real possibility are inexplicably analogous to one another, and fake possibility is insufficiently analogous to them to count as one of them.
That all said, here is a reason why we should hesitate to ascribe monism about metaphysical possibility to Stang’s Kant.Footnote
10
For if we do ascribe monism to Stang’s Kant, it is similarly unclear whether formal possibility understood in Stang’s way really is a species of absolute metaphysical possibility. Even keeping in mind that the P here is restricted to claims about phenomena, do we have a guarantee that P is genuinely metaphysically possible simply because the facts about our forms of experience do not ground ~P?
Here is a kind of hokey example to illustrate the force of this question. Suppose that God’s goodness ensures that the value of the phenomenal is above a certain threshold. Say it has to be at least 1,000 units of goodness; as a matter of necessity, grounded in God’s essence, no phenomenal world less good would be created or sustained. Let P be the claim that the phenomenal world has at least 1,000 units of goodness. Facts about our forms of experience do not ground P; nor do they ground, wholly or partially, ~P. They are wholly compatible with either, as far as I can tell. So it looks like P is formally possible.
So there is a proposition that is formally possible and yet a fact about God’s essence grounds that it is necessarily false. Given monism about metaphysical possibility and Stang’s account of formal possibility, it looks like it can be formally possible that P and yet metaphysically impossible that P. But, assuming that formal possibility is a kind of real possibility and assuming monism about metaphysical possibility, it cannot be formally possible that P and yet metaphysically impossible that P.
If Stang’s Kant is a pluralist about metaphysical possibility, this problem does not arise as clearly. For Stang’s Kant can say that there are two irreducibly different kinds of metaphysical possibility, on one of which P is really possible and on the other of which P is not.
However, one might think that there are important entailments between different kinds of real possibility but be worried that pluralism about real possibility makes it harder to see why these entailments hold. For example, it seems that, if P is formally necessary, then it should also be empirically causally necessary. But it is not clear that Stang’s Kant has the grounds for saying this. To see this, first consider one of Stang’s definitions of empirical-causal necessity:
It is empirically-causally necessary that p if and only if the fact that p is wholly grounded in facts about actual natural laws, and the past history of the empirical world up until time t. (p. 216)Footnote
11
Perhaps one and the same proposition is wholly grounded both in facts about the actual intuitional and conceptual forms and also wholly grounded in facts about the actual natural laws and past history. But it is in no way obvious that this is the case – and it is not obvious that this is even possible. (If P is empirically causally necessary, does this not imply that at most facts about intuitional and conceptual form only partially ground P, since further partial grounds, specifically, material grounds, are also required?) If one and the same proposition cannot have these two sets of whole grounds, then no proposition can be both formally necessary and empirically causally necessary. As mentioned earlier, this strikes me as unfortunate, since I would have thought that every formally necessary proposition is also empirically causally necessary.
4 Pluralism about Real Possibility and Real Essence
In section 2, I discussed a view on which all truths about essences are necessary truths. In section 3, we discussed the advantages and disadvantages of attributing pluralism about real necessity to Kant. In this section, we are going to briefly examine whether a pluralist about real necessity can make sense of the view that all truths about essences are necessary truths.
There are two potential complications that I will mention and then set aside. The first complication is that one might reasonably think that it is not true in full generality that if it is of the essence of x that Fx, then necessarily Fx. One might reasonably think that although it is of the essence of me that I am human, it is not true that necessarily, I am human – since I might have not existed, and I am not human in possible situations in which I do not exist.Footnote
12
Suppose this is the case – still, there is an important connection between essence and necessity. If am essentially human, then, necessarily, I am human if I exist.
The second complication I will set aside concerns pluralism about real essence as well as real necessity. In what follows, I will assume, perhaps uncritically, a kind of monism about real essence – and a kind of monism about ground. However, if there is a 1-1 correspondence between kinds of real necessity and kinds of real essence, it might be that the problem I am concerned with in this section will be easier to answer. Perhaps similar remarks are also true of ground.
Here is the problem: given monism about real essence and pluralism about real necessity, what are the modal consequences of statements of the form □
x
Fx? Suppose it is part of my real essence that I am a human being. Does it follow that it is formally necessary that I am a human being? It is hard to see that it does, since my being a human being is not obviously grounded in facts about intuitional and conceptual form. For one thing, other non-human yet finite creatures might share these intuitional and conceptual forms with humans. (However, that these intuitional and conceptual forms are forms of my intuition and understanding might be grounded in the fact that I am human.) Perhaps that I am a human being is grounded in facts about the laws and the past up to the time of my first moment of existence, and so it is empirically causally necessary that I am a human being. But empirical-causal necessity seems both too weak to be the only kind of necessity engendered by a truth of essence and not the right kind of necessity to be engendered by a truth of essence.Footnote
13
Similar issues arise for grounding. Plausibly, grounding induces necessitation, that is, if P grounds Q, then necessarily, if P then Q. But given pluralism about metaphysical necessity, we need to pause and ask what kind of necessitation grounding induces. If the right response to this question is pluralism about grounding, what kind of grounding was employed in stating each of the various kinds of real necessity?
I am not suggesting that there are no good answers to these questions, but rather that these are the kinds of questions a committed proponent of pluralism about metaphysical necessity, such as Stang’s Kant, should be prepared to address.
Let me close as I began: this is a terrific book, and it repays careful study.Footnote
14
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1 Introduction
It is customary to begin with praise for the author’s book.Footnote 1 And there is much to praise! Nick Stang has written a wonderful book that illuminates many aspects of Kant’s metaphysics, including, but not limited to, his modal metaphysics. It is carefully written, the arguments are tightly constructed, it is historically sensitive and it addresses a centrally important but underexplored aspect of Kant’s philosophy. But even though it is customary to begin with praise, I will not do that, since custom yields merely subjective necessity. Otherwise, I would highly recommend this book to the readers of this journal, and, more generally, to philosophers interested in either metaphysics or the history of philosophy. This book is terrific.
In what follows, I focus on two things. First, in section 2, I discuss a concern about Stang’s interpretation of Descartes. Stang discusses a view that he calls ontotheism and attributes versions of it to several philosophers, including Descartes. The ontotheist is a proponent of the ontological argument. Stang’s Kant takes the ontotheist to be committed to possibilism, the doctrine that there are, or at least could be, non-existent individuals.Footnote 2 But, in my view, his Kant does not discuss the best version of Descartes’ ontological argument. Specifically, I do not think that Descartes’ most promising version of the ontological argument commits him to possibilism.
However, if I am right, this does not show that Stang got Kant wrong. I think that he interprets Kant correctly, but that Kant’s argument is ineffective against Descartes. At the very least though, I’ll get this version of the ontological argument on the table and we can see who, if anyone, misunderstands anyone else.
The second thing I focus on is Stang’s discussions of real possibility. He distinguishes several kinds of real possibility. How do the various kinds of real possibility relate to one another? How do they relate to what contemporary metaphysicians call metaphysical possibility? And how do they relate to adjacent phenomena such as ground and real essence? In section 3, I raise worries about Stang’s formulations of various doctrines of real possibility. In section 4, I preliminarily explore how real essence and ground are connected with the various kinds of real necessity Stang’s Kant recognizes.
2 Descartes and Ontotheism
Ontotheism is the view that God’s essence explains God’s necessary existence. According to Stang, proponents of the ontological argument are ontotheists. And on his interpretation of Kant, Kant thinks that ontotheism entails possibilism. Stang understands possibilism as the view that there are some things that do not exist but could exist. Given possibilism, existence is a determination – it is a feature that some but not all things have. However, Kant argues that existence is not a determination, and so possibilism is false, and hence ontotheism is false.
Although it is controversial whether Descartes was a possibilist, I suspect he probably was not.Footnote 3 More importantly, at least one of his versions of the ontological argument can be formulated even given that possibilism is false.
On the interpretation I favour, the key component of Descartes’ ontological argument is that essence precedes existence.Footnote 4 But it is not part of Descartes’ argument that there are things that merely possibly exist, although he does accept that essences are always possibly exemplified. Here is how I construe the argument. I have a clear and distinct idea of God. Having a clear and distinct idea of x just is grasping the essence of x. But any essentialist statement is necessarily true, independently of whether the possessor of that essence exists; this is the view that essence precedes existence. Since I grasp the essence of God, there is a necessary truth to be grasped about God’s essence. The complete essence of God is that God exists.Footnote 5 Conclusion: so, necessarily, God exists.
On this way of understanding Descartes, claims of the form it is essential to x that Fx can be true even in possible situations in which x does not exist. If we want to regiment the logic of Cartesian essentialist claims, we could use a free logic. (Briefly and roughly, in a free logic, from the fact that Fb, it does not logically follow that something is F.) Stang briefly notes that a version of ontotheism employing a free logic is possible, although not in the context of regimenting Descartes’ views (p. 32, n. 89). He has some things to say about the use of free logic in this sort of context in an online supplement to the book, but I am honestly not sure I understand his response there. We will come back to this momentarily.
In what follows, I will use ‘ □ x ’ as an abbreviation of ‘it of the essence of x that’. The motivation for using a free logic in this context is that it allows us to accept every instance of ‘□ x Fx entails □Fx’ without being committed either to the necessary existence of everything, or to possible things that could exist but do not exist. In general, essentialist truths imply modal truths (and are themselves necessarily true) even though the objects of those essential truths need not necessarily exist. However, when ‘F’ stands for existence, we have an essentialist claim which if true implies the necessary existence of the object of that essentialist claim. This is true even if existence is defined in terms of quantification, that is, even if what it is for x to exist is for x to be identical with something.
In short, on my view, it is the claim that essence precedes existence rather than possibilism per se that does the work in Descartes’ strongest version of the ontological argument. Descartes is not committed to possibilism qua defender of the ontological argument.
As mentioned a few paragraphs back, Stang discusses the use of free logic to defend ontotheism in an online supplement to the book, in which he writes the following:
What then explains the necessary non-emptiness of the name of God? The natural ontotheist view is that ‘God’ is necessarily non-empty because it is essentially the name of God (where the name is individuated semantically rather than orthographically), and God exists necessarily (in virtue of his essence), so ‘God’ necessarily names God and hence is necessarily non-empty. Consequently, I think the ontotheist equipped with a free logic is still forced back upon the basic ontotheist metaphysics (God’s essential existence) to explain the necessary non-emptiness of the name ‘God.’Footnote 6
Let me grant everything in the quoted passage above. I am confused by what comes next. Stang writes:
But if this is correct the ontotheist must give an underlying metaphysics without appealing to the emptiness or non-emptiness of the name of God – because that underlying metaphysics is meant to explain the modal status of names (why some are contingently non-empty and others are necessarily so). Consequently, I think the ontotheist is forced into the same metaphysical conclusions I argue for in the text of the book.
In this context, the relevant metaphysical conclusion is that the ontotheist is committed to possibilism; this is the relevant alleged conclusion, since by ruling out possibilism via the claim that existence is not a determination, ontotheism would also be refuted. But I do not see an explanation of how the ontotheist who employs free logic is committed to possibilism – and hence how Descartes thus regimented would be either. I am hoping Stang can say more here.
Remember why this matters: it is crucial to Kant’s criticism of the ontological argument that existence is not a determination. On the version of Descartes’ ontological argument described earlier, whether or not existence is a determination is irrelevant to the success or failure of that argument.
3 Real Possibility
Let us turn now to Stang’s discussion of real possibility. Kant distinguishes real possibility from logical possibility. A concept is logically possible if and only if the judgement that it has an instance is non-contradictory. But not being contradictory is not sufficient for being really possible.
Contemporary metaphysicians by and large grant this Kantian insight, and accordingly distinguish between metaphysical possibility (or genuine possibility) and logical possibility (or logical consistency). By and large, contemporary metaphysicians understand metaphysical possibility as the widest kind of genuine possibility, and are happy to recognize other kinds of genuine possibility. Something might be such that I can make it actual – and so this something is possible in some more restricted way but is nonetheless metaphysically possible as well. Similarly, to be nomologically possible is to be genuinely compatible with the laws of nature.
On the contemporary way of thinking, each kind of genuine possibility is a restriction on metaphysical possibility, which is the most general kind of genuine possibility. Let K-possibility be a kind of genuine possibility: P is K-possible just in case P is metaphysically possible and X, where the X indicates the additional condition P must meet in order to not be merely metaphysically possible but also K-possible. On the contemporary way of thinking, these different kinds of genuine possibility are kinds of metaphysical possibility in the way that the kinds lion and frog are kinds of animal. Of course there are different kinds of animals – but animal is nonetheless a unitary genus. There are a plurality of animals, but monism about being an animal is nonetheless true. The contemporary view is a kind of monism about metaphysical possibility.
Let us return to Stang’s Kant. Stang tells us that Critical Kant’s term for metaphysical possibility is real possibility. On the Critical Kant’s behalf, Stang also distinguishes various kinds of real possibility. However, unlike the contemporary metaphysician, Stang’s Kant appears to be committed to a kind of pluralism about metaphysical possibility itself. Although Stang is not explicit about this in his book, it seems that his Kant is committed to the claim that there is no such thing as the most general kind of genuine possibility of which each kind of real possibility is a species. There is no overarching unique kind of metaphysical possibility. On such a view, there might be kinds of real possibility K1 and K2 such that P is K1-possibile but K2-impossible, and there is no further fact about whether P is absolutely possible or not. Here is an analogy for understanding Stang’s Kant: just as there is no common genus of which alethic possibility and deontic possibility are species, there is no common genus of which the various kinds of real possibility are species. That said, there might be several formal or substantive features that various kinds of possibility have in common with each other, and these common features might explain why it is reasonable to call each of them ‘real possibility’.
As just mentioned, I think Stang’s Kant is committed to a deep kind of pluralism about metaphysical possibility – although I think much of what Stang says in the book is superficially compatible with monism about metaphysical possibility. Here are some passages to consider.
The various different kinds of real possibility he accepts are unified by a common scheme: real possibilities are grounded in an absolutely necessary first ground. For each kind of real possibility, there is a corresponding conception of an absolutely necessary ground: space (formal possibility), the laws of nature (empirical possibility), real essences (nomic possibility), and God (noumenal possibility). Kant retains his pre-Critical conception of real possibility, generalizes from it to a set of general conditions on any concept of real possibility whatsoever, and then instantiates it at the level of various particular kinds of possibility. (p. 8)
In the Critical philosophy Kant deploys several different kinds of real possibility without explicitly distinguishing them; in this chapter I will distinguish three of them and, in the next chapter, a fourth. What makes all of these different kinds of possibility kinds of real possibility is that they obey Non-Logicality and Groundedness (with modifications to be noted below). (p. 198)
First, it [real possibility] is systematically unified because all of these different kinds of real possibility exhibit a common scheme in virtue of which they are kinds of real possibility. (p. 260)
None of these passages settle by themselves whether to understand Stang’s Kant as a monist or a pluralist about metaphysical possibility. However, as we will see in a moment, there is a good reason to ascribe pluralism to his Kant. That said, Stang (p. 268) does say that the unschematized category of possibility corresponds to the most general kind of real possibility. But this claim is more consonant with monism about metaphysical possibility. Moreover, as suggested by the quote above from p. 198, Critical Kant does not explicitly distinguish various kinds of real possibility – and this fact might engender worries about whether Kant is a pluralist about metaphysical possibility. (If he is a pluralist, why does he not explicitly distinguish various kinds of metaphysical possibility?)
It will be helpful in what follows to quote Stang’s definitions of formal possibility and formal necessity:
(Formal necessity) It is formally necessary that p if and only if the fact that p is wholly grounded in facts about the actual intuitional form (space and time) and conceptual form (categories) of experience. (p. 203)
(Formal possibility) It is formally possible that p if and only if it is not the case that facts about the actual intuitional form (space and time) and intellectual form (unity of apperception) wholly ground the fact that ¬p. (p. 205)
Note that, when discussing whether formal possibility is a kind of real possibility, Stang merely claims that it satisfies several necessary conditions for being a kind of real possibility, but he does not explicitly say that it satisfies any sufficient conditions for being a kind of real possibility.Footnote 7 This would be unproblematic if Stang’s Kant were a monist about metaphysical possibility, for then the sufficient condition for a proposition P to enjoy real possibility of kind K would simply be that P is metaphysically possible and satisfies the stated necessary condition on enjoying K-possibility. In general, a monist about metaphysical possibility has a straightforward criterion of real possibility: all kinds of real possibility entail absolute metaphysical possibility. To see this, consider again nomological possibility. That P is logically consistent with the laws of nature is necessary but not sufficient for P to be nomologically possible. But that P is metaphysically possible and consistent with the laws of nature is necessary and sufficient for P to be nomologically possible. (This is because, on the monist’s view, kinds of real possibility are species of one single genus.) But if Stang’s Kant is a pluralist about metaphysical modality, saying this is not an option. And in this case, if we want to grasp the different kinds of real possibility, we should be unsatisfied with mere necessary conditions that a kind of putative possibility must meet in order to be a kind of real possibility. In fairness to Stang, any kind of pluralist faces a similar question: if you think there are ways of being F, what makes a given G a way of being F? And perhaps, in general, the pluralist can say nothing more illuminating than that the various ways of being F are sufficiently analogous to each other to count as modes of the same overarching yet less specific property.Footnote 8
Relatedly, note that Stang defines the various forms of real possibility and necessity so that they obey analogues of the box/diamond interchange rules in modal logic. That is, for each kind of possibility K, it is K-possible that P if and only if it is not K-necessary that not-P. For example, as you can see in quoted material above, P is formally necessary if and only if not-P is not formally possible. It is plausible that every form of real possibility and its corresponding form of real necessity should obey a box/diamond interchange rule.
However, given how Stang formulates the various kinds of real possibility, strictly speaking, real possibilities need not have grounds for their possibility, but merely require a lack of grounds for their non-actuality. Note that, given the definition of formal possibility above, it is consistent with P’s being formally possible that there is no ground for P period, let alone a ground of the (absolute metaphysical) possibility of P. In general, for any absolutely ungrounded truth P and any kind of real possibility K discussed by Stang, it is K-possible that P. What these observations suggest is that Stang’s account of formal possibility does not capture the idea that formal possibility qua real possibility requires positive grounds for its possibility, not merely an absence of grounds against its actuality.
In general, it does not seem that there is a close connection between the lack of whole grounds for ~P and P’s enjoyment of a kind of real possibility. Consider fake possibility. Say that P is fakely possible if and only if it is not the case that facts about what Donald Trump believes wholly ground the fact that ~p. I assume many propositions are fakely possible. Moreover, fake possibility obeys non-logicality. The non-logicality constraint is that, for any P and kind of real possibility K, it is not a conceptual truth that if it is logically possible that P, then it is K-possible that P. And it is not a conceptual truth that if it is logically possible that P, then it is fakely possible that P. The groundedness constraint is that, if something is fakely possible, it is fakely possible in virtue of how some actual object is.Footnote 9 Fake possibility also meets the groundedness constraint – or at least, it obeys groundedness to exactly the same extent as the other kinds of real possibility as defined by Stang, since all kinds of real possibility satisfy this constraint by way of absence of grounds for falsity rather than presence of grounds for possibility. But I see little reason to think that fake possibility is a kind of real possibility. Sad!
If we were monists about genuine possibility, we could easily deny that fake possibility is a kind of real possibility. But it is less clear how to rule out fake possibility given pluralism about genuine possibility. Perhaps, as noted earlier, the best thing to say is simply that the various kinds of real possibility are inexplicably analogous to one another, and fake possibility is insufficiently analogous to them to count as one of them.
That all said, here is a reason why we should hesitate to ascribe monism about metaphysical possibility to Stang’s Kant.Footnote 10 For if we do ascribe monism to Stang’s Kant, it is similarly unclear whether formal possibility understood in Stang’s way really is a species of absolute metaphysical possibility. Even keeping in mind that the P here is restricted to claims about phenomena, do we have a guarantee that P is genuinely metaphysically possible simply because the facts about our forms of experience do not ground ~P?
Here is a kind of hokey example to illustrate the force of this question. Suppose that God’s goodness ensures that the value of the phenomenal is above a certain threshold. Say it has to be at least 1,000 units of goodness; as a matter of necessity, grounded in God’s essence, no phenomenal world less good would be created or sustained. Let P be the claim that the phenomenal world has at least 1,000 units of goodness. Facts about our forms of experience do not ground P; nor do they ground, wholly or partially, ~P. They are wholly compatible with either, as far as I can tell. So it looks like P is formally possible.
So there is a proposition that is formally possible and yet a fact about God’s essence grounds that it is necessarily false. Given monism about metaphysical possibility and Stang’s account of formal possibility, it looks like it can be formally possible that P and yet metaphysically impossible that P. But, assuming that formal possibility is a kind of real possibility and assuming monism about metaphysical possibility, it cannot be formally possible that P and yet metaphysically impossible that P.
If Stang’s Kant is a pluralist about metaphysical possibility, this problem does not arise as clearly. For Stang’s Kant can say that there are two irreducibly different kinds of metaphysical possibility, on one of which P is really possible and on the other of which P is not.
However, one might think that there are important entailments between different kinds of real possibility but be worried that pluralism about real possibility makes it harder to see why these entailments hold. For example, it seems that, if P is formally necessary, then it should also be empirically causally necessary. But it is not clear that Stang’s Kant has the grounds for saying this. To see this, first consider one of Stang’s definitions of empirical-causal necessity:
It is empirically-causally necessary that p if and only if the fact that p is wholly grounded in facts about actual natural laws, and the past history of the empirical world up until time t. (p. 216)Footnote 11
Perhaps one and the same proposition is wholly grounded both in facts about the actual intuitional and conceptual forms and also wholly grounded in facts about the actual natural laws and past history. But it is in no way obvious that this is the case – and it is not obvious that this is even possible. (If P is empirically causally necessary, does this not imply that at most facts about intuitional and conceptual form only partially ground P, since further partial grounds, specifically, material grounds, are also required?) If one and the same proposition cannot have these two sets of whole grounds, then no proposition can be both formally necessary and empirically causally necessary. As mentioned earlier, this strikes me as unfortunate, since I would have thought that every formally necessary proposition is also empirically causally necessary.
4 Pluralism about Real Possibility and Real Essence
In section 2, I discussed a view on which all truths about essences are necessary truths. In section 3, we discussed the advantages and disadvantages of attributing pluralism about real necessity to Kant. In this section, we are going to briefly examine whether a pluralist about real necessity can make sense of the view that all truths about essences are necessary truths.
There are two potential complications that I will mention and then set aside. The first complication is that one might reasonably think that it is not true in full generality that if it is of the essence of x that Fx, then necessarily Fx. One might reasonably think that although it is of the essence of me that I am human, it is not true that necessarily, I am human – since I might have not existed, and I am not human in possible situations in which I do not exist.Footnote 12 Suppose this is the case – still, there is an important connection between essence and necessity. If am essentially human, then, necessarily, I am human if I exist.
The second complication I will set aside concerns pluralism about real essence as well as real necessity. In what follows, I will assume, perhaps uncritically, a kind of monism about real essence – and a kind of monism about ground. However, if there is a 1-1 correspondence between kinds of real necessity and kinds of real essence, it might be that the problem I am concerned with in this section will be easier to answer. Perhaps similar remarks are also true of ground.
Here is the problem: given monism about real essence and pluralism about real necessity, what are the modal consequences of statements of the form □ x Fx? Suppose it is part of my real essence that I am a human being. Does it follow that it is formally necessary that I am a human being? It is hard to see that it does, since my being a human being is not obviously grounded in facts about intuitional and conceptual form. For one thing, other non-human yet finite creatures might share these intuitional and conceptual forms with humans. (However, that these intuitional and conceptual forms are forms of my intuition and understanding might be grounded in the fact that I am human.) Perhaps that I am a human being is grounded in facts about the laws and the past up to the time of my first moment of existence, and so it is empirically causally necessary that I am a human being. But empirical-causal necessity seems both too weak to be the only kind of necessity engendered by a truth of essence and not the right kind of necessity to be engendered by a truth of essence.Footnote 13
Similar issues arise for grounding. Plausibly, grounding induces necessitation, that is, if P grounds Q, then necessarily, if P then Q. But given pluralism about metaphysical necessity, we need to pause and ask what kind of necessitation grounding induces. If the right response to this question is pluralism about grounding, what kind of grounding was employed in stating each of the various kinds of real necessity?
I am not suggesting that there are no good answers to these questions, but rather that these are the kinds of questions a committed proponent of pluralism about metaphysical necessity, such as Stang’s Kant, should be prepared to address.
Let me close as I began: this is a terrific book, and it repays careful study.Footnote 14