The Australian philosopher John Passmore (1914 – 2004) is described in his Telegraph obituary as "an Andersonian radical, swept away, though not to the point of unquestioning devotion, by his Scottish-born philosophy professor, John Anderson . . . ." The influence of Anderson on Passmore is very clear from the latter's Philosophical Reasoning (Basic Books, 1969; orig. publ. 1961). The Andersonian Chapter Three, "The Two-Worlds Argument," is the cynosure of my current interest, in particular, the distinction Passmore makes between what he calls entity-monism and what he calls existence-monism. (Anderson, as far as I know does not use these terms and, as far as I know, they have found no resonance among the epigoni. The terms are not found in the index of A. J. Baker's Australian Realism: The Systematic Philosophy of John Anderson, Cambridge UP, 1986. And Quentin Gibson, The Existence Principle, Kluwer, 1998, p. 14, dismisses 'existence-monism' as a misleading label for Anderson's view.)
In this entry I will present the distinction and then comment critically upon it.
Passmore tells us that
Entity-monism is the doctrine that 'ultimately' there is only one real entity. What we normally regard as distinct things — whether they be chairs, or musical compositions, or human being — are, all of them, appearances of this one entity. (38)
[. . .]
Existence-monism is difficult to define in general terms. But we might put it thus: when we say that something exists, or that things of a certain kind exist, this exist or exists has an invariant meaning whatever the 'something' or the 'kind' may be, i.e. there are not sorts, or levels, or orders of existence. More accurately, what is asserted by 'X exists' can always be asserted by a proposition which contains an 'is' which has, in this sense, an invariant meaning. Existence-monism, unlike entity-monism, does admit of varieties. Philosophers might say, and have said, that to exist is to be perceived, or to be in process, or to be spatiotemporal, or to be a possible subject for physical investigation, or to be a thing with properties, and do on. (39, bolding added)
I have two criticisms.
1. There is first of all a slide from a semantic thesis, a thesis about meaning, to an ontological thesis, a thesis about being. Passmore conflates the semantic claim that 'exists' and cognates have an invariant meaning or sense with the ontological claim that there are no sorts or kinds or levels or orders or modes or ways of being/existence. But as I see it, one can consistently maintain both that (i) 'exists' and cognates is univocal in sense across all its uses and that (ii) there are different modes of existence. For this reason, (i) and (ii) are distinct theses.
Let me give a quick illustration. Carpets exist and bulges in carpets exist. In the sentence immediately preceding 'exist' is invariant in sense across both occurrences (both tokenings). And yet it makes good sense to say that carpets and bulges exist in different ways. A carpet can exist with or without a bulge; but no carpet bulge can exist without a carpet whose bulge it is. If a substance is defined as an entity logically capable of independent existence, then a carpet is a substance. But surely no bulge in a carpet is a substance. For no carpet bulge is logically capable of independent existence. It is rather an accident of the carpet as substance. Carpet and bulge exist in different ways: the carpet exists in itself; the bulge in another. Or: the carpet exists independently; the bulge dependently. To think of carpet and bulge as Humean "distinct existences" strains credulity. What we have here are not two Hume-distinct items that stand in a causal relation. Nor do they stand in a logical relation if such relationsd are defined over propositions. What we have here is irreducible existential dependence: the bulge depends in its existence upon the carpet, but not vice versa. To make sense of this example we need to speak of two different modes of existence.
Suppose you accept this. Surely the acceptance is logically consistent with saying that both carpets and bulges exist in the same sense of 'exist.' And what sense is that? It is the sense expressed by the so-called existential quantifier. A better name for it is 'particular quantifier.' In 'Some items are carpets' and 'Some items are bulges,' the predicate 'Some items are ___' has the same sense. And yet carpets and bulges, like faces and smiles, exist in different ways. Or at least one can with no breach of logical consistency maintain this ontological thesis while also holding to the semantic univocity of 'exists' and cognates. Just don't confuse the ontological with the semantic. Don't confuse ways of existing with senses of 'exists.'
Well, I hope you followed that. Now on to the second criticism where the going gets tougher.
2. Passmore clearly sees that one could not sensibly maintain that to be = to be water. "Nobody could now win credence who asserted that to be is to be a quantity of water, however plausible that doctrine might have looked to Thales." (39) And the reason would not be that we now know that water is not an element, or that there are stuffs other than water. The reason lies deeper. If to exist is to be water, then 'Water exists' would be equivalent to the tautology 'Water is water,' when it obviously isn't.
It seems clear that there is no kind of thing or kind of stuff that we could invoke to give descriptive content to existence in general. There is no K such that it will come out true that to be = to be a K or a quantity of K. No one will maintain that to be is to be a lump of coal or to be a cat or to be a quantity of hydrogen. There are two problems here. First, if to be = to be a K, then only Ks could exist. If to be is to be a cat, then only cats could exist: everything would be a cat. Not good! Second, even if there is some K that everything is, being K and existing are not the same. For to say that Ks exist is not to say that Ks are Ks.
What about: to be is to be spatiotemporal? One problem with this naturalist proposal is that it is circular. A thing cannot be spatiotemporal unless it exists in space-time. But then the proposal comes to this: for x to exist is for x to be spatiotemporal and exist. This point about circularity is equivalent to the second point I just made. To say of a spatiotemporal thing that exists is not to say that it is spatiotemporal. To give it a modal twist: it is necessary that spatiotemporal items be spatiotemporal, but contingent that any exist.
So it comes as a surprise when Passmore says, with respect to "To be is to have a place in Space-Time," that "this sort of difficulty does not arise," namely the difficulty in the water example. Why not? Because, "Space-Time is not the sort of thing to which existence is ascribed or which is used to distinguish one thing from another." (39) But surely we do ascribe existence to spacetime. And it is question-begging to say that spatiotemporality does not distinguish one thing from another: it distinguishes concrete things from abstract things. Granted, it does not distinguish items in space time, but neither does being a cat distinguish cats from one another.
So is seems to me that 'To be is to be water' and 'To be is to be spatiotemporal' are on a par. The only difference is that 'water' picks out a natural stuff-kind while 'spatiotemporal pickls out a mode of being.
Pace Anderson and Passmore, being cannot be identified with being spatiotemporal.
What then becomes of existence-monism? Existence-monism amounts to the claim that there is a single way of being or existence as opposed to two or more ways. Thus existence-monism is taken by Andersonians to rule out Plato's two-world theory according to which Forms exist atemporally while the phenomenal particulars that participate in them exist in a temporal way. But as I pointed out in my first criticism, one cannot validly infer a single way of being from a single use of 'exists.' Univocity at the level of sense doesn't entail modal sngleness at the level of being.
What reason, then, do we have to think that there is a single way of being? Well, you might say that it is evident to the senses that there are things in space and time. Fine, but that doesn't show that there is a way of being that is their way of being, even with the addition of the premise that everything that exists exists in space and time. That is, it does not show that we must distinguish between nature, existence, and mode of existence. Why can't we eke by with just nature and existence?
Besides, if there is exactly one way of being, and spatiotemporal items, which we know to exist, exist in that way, does it not follow that to be = to be spatiotemporal, that existence reduces to spatiotemporality? But we saw above under #2 that that can't be right: there is no F such that to exist = to be F. (Wel, there is one case, but it is a very specila one idneed!)
I suspect that we cannot speak of a way of being at all unless we speak of two or more ways of being. For what could motivate the tripartite distinction among nature, existence, and mode, if not examples like that of the carpet and the bulge where it is highly plausible to say that the items distinguished exist in diferent ways? I am assuming that one has not made the mistake exposed in #1 above, namely, the mistake of confusing senses and modes and sliding illicitly from the univocity of 'exists' to the singleness of mode of being.
There are three positions that want distinguishing:
Existence-Monism: There is exactly one mode of being.
Existence-Pluralism: There are two or more modes of being.
Existence-Nihilism: There are no modes of being.
The real debate is between the pluralists and the nihilists. The monist position of the Andersonians is the result of confusion. Or at least that is the way it looks at the moment. But we press on.

From a comment thread:
Here is an excerpt from a forthcoming article of mine to appear in a volume honoring the late David M. Armstrong, widely regarded as Australia's greatest philosopher:
II. The Truth-Maker Argument for Facts
The central and best among several arguments for facts is the Truth-Maker Argument. Take some such contingently true affirmative singular sentence as 'Al is fat.' Surely with respect to such sentences there is more to truth than the sentences that are true. There must be something external to a true sentence that grounds its being true, and this external something is not plausibly taken to be another sentence or the say-so of some person. 'Al is fat' is not just true; it is true because there is something in extralinguistic and extramental reality that 'makes' it true, something 'in virtue of which' it is true. There is this short man, Al, and the guy weighs 250 lbs. There is nothing linguistic or mental about the man or his weight. Here is the sound core, at once both ancient and perennial, of correspondence theories of truth. Our sample sentence is not just true; it is true because of the way the world outside the mind and outside the sentence is configured. The 'because' is not a causal 'because.' The question is not the empirical-causal one as to why Al is fat. He is fat because he eats too much. The question concerns the ontological ground of the truth of the sentential representation, 'Al is fat.' Since it is obvious that the sentence cannot just be true — given that it is not true in virtue of its logical form or ex vi terminorum — we must posit something external to the sentence that 'makes' it true. I don't see how this can be avoided even though I cheerfully admit that 'makes true' is not perfectly clear. That (some) truths refer us to the world as to that which makes them true is so obvious and commonsensical and indeed 'Australian' that one ought to hesitate to reject the idea because of the undeniable puzzles that it engenders. Motion is puzzling too but presumably not to be denied on the ground of its being puzzling.
Now what is the nature of this external truth-maker? If we need truth-makers it doesn't follow straightaway that we need facts. This is a further step in the argument. Truth-maker is an office. Who or what is a viable candidate? It can't be Al by himself, if Al is taken to be ontologically unstructured, an Armstrongian 'blob,' as opposed to a 'layer cake,' and it can't be fatness by itself.1 (Armstrong 1989a, 38, 58) If Al by himself were the truth-maker of 'Al is fat' then Al by himself would make true 'Al is not fat' and every sentence about Al whether true or false. If fatness by itself were the truth-maker, then fatness exemplified by some other person would be the truth-maker of 'Al is fat.' Nor can the truth-maker be the pair of the two. For it could be that Al exists and fatness exists, by being exemplified by Sal, say, but Al does not instantiate fatness. What is needed, apparently, is a proposition-like entity, the fact of Al's being fat. We need something in the world to undergird the predicative tie. So it seems we must add the category of fact to our ontology, to our categorial inventory. Veritas sequitur esse – the principle that truth follows being, that there are no truths about what lacks being or existence – is not enough. It is not enough that all truths are about existing items pace Meinong. It is not enough that 'Al' and 'fat' have worldly referents; the sentence as a whole needs a worldly referent. In many cases, though perhaps not in all, truth-makers cannot be 'things' – where a thing is either an individual or a property – or collections of same, but must be entities of a different categorial sort. Truth-making facts are therefore 'an addition to being,' not 'an ontological free lunch,' to employ a couple of signature Armstrongian phrases. For the early Armstrong at least, facts do not supervene upon their constituents. This yields the following scheme. There are particulars and there are universals. The Truth-Maker Argument, however, shows or at least supports the contention that there must also be facts: particulars-instantiating-universals.2 There are other arguments for facts, but they cannot be discussed here. And there are other candidates for the office of truth-maker such as tropes and Husserlian moments (Mulligan et al. 2009) but these other candidates cannot be discussed here either. Deeper than any particular argument for facts, or discussion of the nature of facts, lies the question whether realism about facts even makes sense. To this question we now turn.
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1If Al is a blob, then he lacks ontological structure; but that is not to say that he lacks spatial or temporal parts. It is obvious that he has spatial parts; it is not obvious that he has ontological 'parts.' Thin particulars, properties, and nexus count as ontological 'parts.' Layer cakes have both spatiotemporal and ontological structure.
2Are facts or states of affairs then a third category of entity in addition to particulars and universals? Armstrong fights shy of this admission: “I do not think that the recognition of states of affairs involves introducing a new entity. . . . it seems misleading to say that there are particulars, universals, and states of affairs.” (Armstrong 1978, 80) Here we begin to glimpse the internal instability of Armstrong's notion of a state of affairs. On the one hand, it is something in addition to its constituents: it does not reduce to them or supervene upon them. On the other hand, it is not a third category of entity. We shall see that this instability proves disastrous for Armstrong's ontology.