Author: Bill Vallicella

One commenter seems not to understand the problem as I set it forth here. So let's take a few steps back.  In this entry I explain terminology, make distinctions, and record assumptions.  

1) Everything actual is possible, but the converse does not follow and ought not be assumed. Possible items that are possible, but not actual, are called 'merely possible.'  Mere possibles are also sometimes referred to as 'unrealized possibles' or 'unrealized possibilities.'

2) Don't confuse the reality of a mere possible with its realization (actualization). A mere possible can be real without being realized just as a proposition can exist without being true.  Indeed, if mere possibles are real, then they are precisely not realized; else they would not be mere possibles.

3) Don't confuse the possibility of a mere possible with the possible itself. Mere possibles are presumably many; their possibility (their being-possible) is presumably one and common to them all. Analogy: there are many true propositions, but their truth is presumably one and common to them all.

4) Don't confuse reality with actuality. The reality of mere possibles is obviously not their actuality. Everything actual is real, but the converse does not follow and we ought not assume it.    

5) In (1) above I used 'item.' 'Item' is the most noncommittal word in my philosophical lexicon.  It is neutral with respect to categorial status, modal status, and ontological status.  Are there nonexisting items? My use of 'item' leaves this question open in the way that 'Are there nonexistent existents?' does not.  Even though 'item' should remind you of the Latin idem, my use of 'item' is so liberal and latitudinarian that it does not rule out the self-diverse item, which is a bona fide item in some Meinongian systems.

One must be careful in one's terminological choices to neither beg questions nor bury them.

6) My present concern is with real, not epistemic or doxastic, possibility. Roughly, the  epistemically/doxastically  possible is that which is possible given what I know/believe. The really possible — which divides into the actual and the merely possible — is that which is possible whether or not any knowers/believers exist.  The really possible does not depend on our knowledge or ignorance. To go into a bit more detail:

In ordinary English, epistemic uses of 'possible' are rife.   I inquire, "Is Jones in his office?" The secretary replies, "It's possible." I am not being informed that Jones' presence in his office is consistent with the laws of logic, or with the laws of nature; there is no question about the logical or nomological possibility of Jones' being in his office.   I am being informed that Jones' presence in his office is consistent with what the secretary knows: it is not ruled out by anything she knows.  It's possible for all she knows.  Of course, if the secretary knows that Jones is in his office, or knows something that (she knows) entails that he is in his office, then Jones' presence in his office will be logically consistent with what she knows; but in that case she will not say that it is possible that he be there. She will say, "He's there."  So 'possible' in its epistemic use conveys both consistency with what one knows and ignorance. When I say that such-and-such is epistemically possible, I am saying that it is possible for all I know, but I don't know all about the matter in question. Letting 'S' range over states of affairs and 'P' over persons, we define

D1. S is epistemically possible for P =_df (i) S is logically consistent with what P knows; (ii) S is neither known by P nor known to be entailed by anything P knows.

The reason for clause (ii) is that epistemic uses of 'possible' indicate ignorance. 'It's possible that Jones is in his office,' said by the secretary implies that she does not know whether or not he is in his office.  If she knew that he was in his office, and said what she said, then she would not be using 'possible' in the epistemic way it is used in ordinary English.

7) I take it to be a datum that there are real mere possibilities. For example, at the moment there is exactly one cat in my study. But there might have been two or there might have been none.  The latter two states of affairs are both merely possible and real.  They are merely possible because they are not actual. They are really possible because the possibility of these mere possibles is not parasitic upon anyone's knowledge or ignorance.   The possibles are 'out there,' part of the 'furniture of the world.' Again, the possibility or being-possible of a mere possible is not to be confused with the merely possible item itself. 

8) My writing table is now two inches from the wall. But it might have been now three inches from the wall, where 'now' picks out the same time in both of its most recent occurrences. The table might have been infinitely other distances from the wall as well.  How do I know that? This question pertains to the epistemology of modal knowledge and is off-topic. The present topic is the ontology of the merely possible.  This meditation assumes, or rather takes as a datum, the reality of the merely possible.  Notoriously, however, one man's datum is another man's theory.

9) If there are real mere possibles (individuals, states of affairs . . .), then reality is not exhausted by the actual; it includes both the actual and the merely possible.  If it were so exhausted, all would be necessary, and nothing would be contingent.  The modal distinctions would remain on the intensional plane, but would find no purchase in fact. We would have the extensional collapse of the modal distinctions. Can I prove that there is no such collapse? No.

10) 'Possible' has several senses.  Chief among them are the logical, the metaphysical, and the nomological or physical. The following Euler –not Venn! — diagram shows how they are related:

This is a large topic by itself. I will just say for present purposes that the ontological problem of the merely possible is concerned  with mere possibles the possibility of which is metaphysical, where the metaphysically possible is that which is admissible both by the laws of formal logic and by the laws of metaphysics.  Here is a candidate law of metaphysics: everything that exists has properties. This is not a formal-logical truth inasmuch as its negation — Something that exists has no properties — is not a formal-logical contradiction.   

11) The examples I have given above involving cats and rooms and tables and walls are merely possible state of affairs involving actualia. For example, my torso is now covered with a shirt, but it might not now have been covered with that shirt or any shirt.  Torso and shirt are constituents of an actual and of a merely possible state of affairs, respectively.  But there are possibilia that do not involve actualia.  Let n = the number of actual cats at time t.  Could there not have been n + 1 actual cats at time t?  Surely that is possible. Deny it and you are saying that it is necessary that the number of actual cats at t  be n.  Do you want to say that? In this example, the mere possibility does not involve actualia in the way the mere possibility of my cat's sleeping now involve an actual cat.  You might tell me that the actual world is such that it might have now contained one more cat than it in fact now contains, and so the actual world is the actual item involved in the possibility. Maybe, maybe not. How about the possibility that nothing at all exist? I have argued in these pages that there is no such possibility as the possibility of there being nothing at all. But if there is this possibility, then it is not one that is grounded in, or presupposes, any actual item.

12) Now to the problem.  As I wrote earlier,

. . . the problem of the merely possible is something like this.  Merely possible individuals and states of affairs are not nothing, nor are they fictional.  And of course their possibility is not merely epistemic, or parasitic upon our ignorance.  Merely possible individuals and states of affairs have some sort of mind-independent reality.  But how the devil can we make sense of this mind-independent reality given that the merely possible, by definition, is not actual?  Suppose we cast the puzzle in the mold of an aporetic triad:

a. The merely possible is not actual.

b. The merely possible is real (independently of finite minds).

c.  Whatever is  real is actual.

Clearly, the members of this trio cannot all be true.  Any two of them, taken in conjunction, entails the negation of the remaining one.  For example, the conjunction of the last two propositions entails the negation of the first.

Steven Nemes comments:

I would think that once you've admitted the reality of the merely possible, contrary to your (c) above, you've answered the question. The merely possible represents an irreducible ontological category and that's that. Why not?

The Nemes solution is to reject (c).  Accordingly, mere possibles are an irreducible category of beings. This is a version of possibilism, as opposed to actualism, in the metaphysics of modality. One response to Nemes is that the mere admission of the reality of the merely possible does not suffice to establish possibilism.  For the actualist too admits the reality of the merely possible but without admitting that mere possibles constitute an irreducible ontological category. The fact that there is a long-standing and ongoing debate between possibilists and actualists shows that one cannot take the reality of the merely possible to settle the question.