THE PLATONIST ARGUMENT FOR CAUSAL NECESSITARIANISM
OVERVIEW
I use the term ‘causal necessitarianism’ to refer to the view that causal laws are
metaphysically necessary. It is well known that the causal theory of properties endorsed by Sydney
Shoemaker and others entails causal necessitarianism.1 This paper will show that there are reasons
for being a causal necessitarian even if the causal theory of properties is not correct. It will be shown
that if Platonism is true and there is a nomological requirement on causation, then causal
necessitarianism is true. The view I shall call ‘Platonism’ is the doctrine that (i) properties necessarily
exist and (ii) there are (or can be) uninstantiated properties. The nomological requirement on
causation states that causal relations obtain between events in virtue of instantiating a causal law.
Platonism and the nomological requirement on causation will be discussed in greater detail in
what follows. Before discussing them, I shall articulate the Platonist argument for causal
necessitarianism. An explanation of the argument will follow. Some objections to the argument will
be considered and rebutted.
THE ARGUMENT
P1. Platonism is true. (Premise)
P2. There is a nomological requirement on causal relations. (Premise)
P3. Relations between necessary existents obtain necessarily (and descriptions of these relations are
metaphysically necessary). (Premise)
P4. An analytic consequence of (P2) is that causal laws are relations between properties.
P5. An analytic consequence of (P1) is that properties necessarily exist.
Shoemaker (1984) and Shoemaker (1998) both defend the causal theory of properties. Zimmerman (2000) provides a
critical treatment of Shomaker’s view.
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P6. By (P3), (P4), and (P5), causal laws obtain necessarily, and causal law-statements are
metaphysically necessary. That is, causal necessitarianism is true!
The above argument is valid, but is it sound? One difficulty in assessing its soundness is that
each premise is a general metaphysical principle, and such principles often do not inspire
confidence. (P1), (P2), and (P3) will be explained in the following three sections. A full-blown
defense of these claims will not be provided. It is far beyond the scope of this paper to establish the
truth about universals and causation!
EXPLANATION OF (P1)
This section will remark on my use of Platonism in the above argument. ‘Platonism’ is an
appropriate name for the view to which it refers, because it is helpfully contrasted with the
“Aristotelian” view that (i) properties contingently exist and (ii) all properties must be instantiated.
Platonists hold that properties are abstract entities, and abstract entities both necessarily exist and
may not be instantiated.
A thorough-going Platonism that takes all properties to necessarily exist is not required for
the above argument to be valid. A mitigated form of Platonism that does not take all properties to
necessarily exist can support my argument for causal necessitarianism. This form of Platonism must
hold that all properties that are involved in causal laws necessarily exist. This version of Platonism could
hold that there are some contingently existing properties but these properties are not involved in
causal laws.
Why would someone contend that some properties necessarily exist and others contingently
exist? Alvin Plantinga, in “On Existentialism” discusses the “existentialist” thesis that quidditative
properties (i.e. properties that are thissnesses or involve thisnesses) contingently exist. He notes that an
existentialist might take qualitative properties (e.g. the property of being a barn) to necessarily exist.
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We can see that existentialism is consistent with the type of Platonism required for my argument for
causal necessitarianism. If an existentialist (in the Plantigian sense) accepts the necessary existence of
qualitative properties and holds that only qualitative properties stand in causal relations, then she can
accept the Platonist argument for necessitarianism. In short, the Platonist argument for
necessitarianism is consistent with the claim that some properties contingently exist.
The rest of this section will briefly discuss some of the metaphysical ramifications of
accepting Platonism. Platonism is not consistent with (and must deny!) the principle of instantiation.
The principle of instantiation claims that there are no uninstantiated properties. David Armstrong,
in What is a Law of Nature?, states some of the strongest motivations for adopting the principle of
instantiation. He says,
A major reason for accepting the Principle of Instantiation is my desire to uphold,
along with Realism about universals, the logically independent doctrine of
Naturalism. Naturalism I define as the view that nothing else exists except the single,
spatio-temporal world, the world studied by physics, chemistry, cosmology and so
on. (82)
Naturalism naturally (pun intended) accompanies Armstrong’s “Actualism.” Actualism is the view
that the only things that exist are things that actually exist. This view maintains that (a) nothing is
merely possible and (b) dispositions and causal powers are “always found in” the actual properties of
objects. (8) In sum, actualism and naturalism entail the principle of instantiation, which in turn
entails that Planonism is false.
It is worth noting that all of these doctrines (naturalism, actualism, the principle of
instantiation and Platonism) are either necessarily true or necessarily false. It is obvious that
Platonism is inconsistent with naturalism, actualism, and the principle of instantiation. Since it is not
a goal of this paper to defend Platonism, I shall not discuss these views any further. I merely
mention them to give a sense of the ontological cost of Platonism. It is beyond the scope of the
paper to show that Platonism is worth the price.
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EXPLANATION OF P2
(P2) claims that there is a nomological requirement on causal relations.2 In Mind in a Physical
World, Jaegwon Kim characterizes the nomological requirement as holding that events standing in
causal relations must instantiate a causal law. (33) Following Kim’s characterization of the
nomological requirement on causation, we can understand the nomological requirement on causal
relations to hold that event causation occurs in virtue of properties that are related by causal laws.3
That is, events exemplify causal relations insofar as those events instantiate properties that are
involved in causal laws. For instance, when the occurrence of a neural state causes the occurrence of
a phenomenal state, we can take a causal relation to obtain between these events in virtue of the fact
that these states exemplify properties that are related by a causal law.
In order to avoid confusion, it is useful to distinguish causal laws from causal lawstatements. Causal laws are de re necessities that obtain between properties. Specifically, they are
dyadic relations that obtain between properties. More formally, events a and b stand in a causal
relation if and only if there is a causal law N that obtains between properties a* and b*, where a* is a
constituent property of a and b* is a constituent property of b. (This characterization of nomic
necessitation closely follows Armstrong (1983). I agree with Armstrong’s contention that “In the
end… the relation of nomic necessitation N will have to be accepted as a primitive.” (88)) Lawstatements are propositions that describe causal laws. Causal laws are the ontological grounds for
(i.e. the “truth makers” for) the law statements. 4
The nomological requirement on causation is accepted, while developed in different ways, in Armstrong (1983) and
Sosa (1993).
3 Armstrong (1983) notes that the nomological requirement on causation assumes realism about properties/universals.
(8) Hence, if (P2) is true, anti-realist criticisms of Platonism cannot undermine (P1).
4 By distinguishing laws from law-statements I follow Armstrong (1983): “Law-statements may be true or (much more
likely) be false. If they are true, then what makes them true is a law.” (8)
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No objections will be raised against the nomological requirement on causation in what
follows. Causal necessitarianism presupposes the nomological requirement on causation because it
presupposes that there are causal laws. Thus, if (P2) is false, causal necessitarianism is a non-starter.
EXPLANATION OF P3
(P3) claims that relations between necessary existents obtain necessarily (and it states that
descriptions of these relations are metaphysically necessary). As it stands, (P3) needs further
clarification. Since a relation between a necessary existent and a contingent existent is a contingent
relation (e.g. if the number five stands in the being thought about relation to Joe, we can see that the
being thought about relation is contingent), we need to restrict the principle to relations whose relata
are necessary existents.
(P3) can be clarified as follows: a relation that obtains between nothing but necessary existents
must obtain necessarily. The following quotes from Evan Fales and David Armstrong support the
intuition behind this principle. Fales, in Causation and Universals, says, “I suspect that every truth
about relations among universals is a necessary truth; but I know of no way of proving this….”
(footnote 18, 333) In a similar vein, Armstrong (1983):
One might invoke the principle: if the terms of a relation involve nothing but
necessary beings then the relation itself must hold necessarily. This principle has
some plausibility. Apparently obvious counter-examples, such as co-instantiation by
particulars, fail to respect the condition that the term of the relation involve nothing
but necessary beings. However, I do not know how to give positive arguments for
this principle. (footnote 1, 164, 165)
Like Fales and Armstrong, I doubt that a proof will be offered for the principle in question. However,
I think that some considerations can be raised in favor of it.
First, the principle that relations between nothing but necessary existents are necessary
supports our intuition that mathematical relations, which are relations between necessary existents,
are metaphysically necessary. Just as descriptions of relations between numbers are metaphysically
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necessary and eternal (e.g. ‘3 < 4’ expresses an eternally true metaphysical necessity), descriptions of
relations between properties are metaphysically necessary.
Secondly, (P3) is supported by the intuitive idea that particulars change but universals don’t.
Particulars are created, they can be destroyed, and they are in time (as opposed to being eternal).
Relations between particulars are contingent, because they are prone to change. Since relations
between universals are immutable and eternal, there is prima facia evidence that those relations are
necessary. Of course, the fact that something is immutable doesn’t entail that it necessarily exists. For
example, it may be an eternal and immutable truth that I’m sitting in front of my desk at home at
8:00 on May 1, 2004, but that truth is not metaphysically necessary. I could have been elsewhere at
that time. In sum, although the fact that something is immutable and eternal does not entail that it is
metaphysically necessary, the fact that something is immutable and eternal intuitively gives a reason to
posit its necessary existence.
OBJECTION TO P1
One objection that is relevant to the Platonist theory of properties in this context is that it
this kind of Platonism consistent with the existence of nomic necessities obtaining between
uninstantiated properties. The existence of such relations might seem to undermine Platonism,
because it seems grossly implausible accept a view that allows a causal law to obtain between
uninstantiated properties. That is, a theory of causation loses a great deal of plausibility if it is
consistent with there being genuine causal relations between say, the property of being Scooby
snacks and the property of satiating Scooby’s hunger. I will grant that Platonism is consistent with
the existence of uninstantiated properties being related by nomic necessities. However, the mere
consistency of these claims does not establish that the causal necessitarian has any reason to think
that causal laws hold between any particular uninstantiated properties.
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A Platonist causal necessitarian can hold that there is no reason for thinking that causal laws
obtain between certain uninstantiated properties. Here are two reasons in support of this claim.
First, a Platonist causal necessitarian might hold that causal laws only obtain between properties that
are instantiated. That is, a Platonist might accept a principle of instantiation for all properties that
stand in causal relations: all properties that are involved in causal laws must be instantiated. Since
Platonism, unlike the causal theory of properties, is consistent with holding that some properties
exist that do not play a role in the causal nexus (i.e. since a Platonist causal necessitarian might hold
that some properties are not causally related to other properties), a Platonist can consistently say that
there are uninstantiated properties but none of them are involved in causal laws. Secondly, when a
causal law is alleged to hold between certain properties, this alleged causal law is justified by
observation (causal laws are a postiori necessities). Relations between uninstantiated properties cannot
be observed. Thus, there cannot be any reason for posting causal laws to obtain between any
specific uninstantiated properties.
In short, Platonist causal necessitarians have no reason to hold that any particular uninstantiated
properties are involved in causal laws.
OBJECTIONS TO P3
Above three considerations were raised in favor of (P3). Objections will be raised against
each these considerations in turn. First, one might contend that there is an important disanalogy
between mathematical statements and causal law statements. The dissimilarity between these types
of statements flows from the fact that we cannot conceive that mathematical statements are false but
we can conceive that certain causal laws fail to obtain. Thus, we should not take causal lawstatements to be metaphysically necessary.
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It should be noted that this objection applies to both (P3) and causal necessitarianism. For
any causal law that obtains, it seems that we can conceive that there is some possible world where it
doesn’t obtain. I will provide a few brief comments that might ease worries that result from this style
of objection. In this context I take ‘conceive’ and its cognates to be success terms. That is, if
someone conceives that a proposition P is true, then is possible that P. Alternatively, if P is conceivable,
then it is possible that P.5
I grant that someone might seem to conceive that a genuine causal law fails to obtain.
However, seeming conceivability does not entail possibility. Moreover, we lack an introspective
capacity to distinguish propositions that merely seem to be conceivable from propositions that are
genuinely conceivable. I am not making the bold assertion that seeming conceivability is not a
reliable guide to possibility in general.6 I am merely pointing out that we do not have infallible
introspective evidence of possibility. Furthermore, when we step into the domain of a postiori
necessities, there is less reason to trust our conceivability evidence7 (by ‘conceivability evidence’ I
mean the apparent conceivability of a proposition). Since (i) we rely on non-introspective methods
in order to establish a posteriori necessities and (ii) causal necessitarians take the discovery of causal
laws to be the discovery of a posteriori necessities, it follows that (iii) causal necessitarians do not need
to be concerned about conceivability evidence that opposes causal necessitarianism. Conceivability
evidence is a deliverance of introspection, and introspection does not tell us whether a proposition is
an a posteriori necessity.
Secondly, in defense of (P3) it was suggested above that the immutability of universals and
the causal laws that involve them lends credence to the metaphysical necessity of the causal law
The conditionals in the last two sentences of this paragraph express strict implication.
Yablo (1993) points out an analogy between the reliability of perception and the reliability of conceivability evidence.
He contends that it would require a very strong argument to establish that seeming conceivability is not in general a
reliable guide to possibility.
7 Van Inwagen (1998) argues that conceivability evidence is not a reliable guide to possibility. He observes that many
propositions that appear possible to us involve a posteriori necessities about the underlying molecular facts about the
macro-level objects involved in the apparent possibility. For the sake of brevity, I will not discuss this point any further.
5
6
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statements. It was noted above that the immutability of a being does not entail that its existence is
metaphysically necessary and someone might find it hard to see the sense in which considerations
about the immutability of a being lends credence to claims about its necessary existence. After all,
one might stress, it must be acknowledged that the intuitiveness of an inference is not a reliable
indicator of its cogency—consider “the gambler’s fallacy.”
I grant that the immutability and eternal existence of a being does not entail that its existence
is metaphysically necessary. However, we often have reasons for believing things when those reasons
do not entail what they support. There is a strong intuition that if something is immutable and eternal,
then there is reason to think that it is metaphysically necessary. As Shoemaker says in “Causal and
Metaphysical Necessity”, intra-world invariance suggests inter-world invariance. Although this move
is not legitimated by logical entailment, it does seem reasonable.
CONCLUDING REMARKS
One unique feature of the Platonist argument for causal necessitarianism is that it supports
causal necessitarianism without assuming that properties are individuated by their causal powers.
The Platonist argument also does not assume that properties have their causal powers essentially.
Rather, it shows how causal necessitarianism can be supported with a Platonic theory of properties.
“The Platonist Argument for Causal Necessitarianism”
WORKS CITED
Armstrong, David. (1983) What is a Law of Nature? Cambridge: Cambridge University Press.
Fales, Evan. (1990) Causation and Universals. London: Routledge.
Kim, Jaegwon. (2000) Mind in a Physical World. Cambridge: MIT Press.
Plantinga, Alvin. (1983) “On Existentialism.” Philosophical Studies. 44. pp.313-329.
Shoemaker, Sydney. (1984) “Causality and Properties.” in Identity, Cause, and Mind.
Cambridge: Cambridge University Press. 234-60.
. (1998) “Causal and Metaphysical Necessity.” Pacific Philosophical
Quarterly. 79:
59-77.
Sosa, Ernest. (1993) “Varieties of Causation” in Causation (eds. Ernest Sosa and Michael
Tooley) Oxford: Oxford University Press.
Yablo, Stephen. (1993) “Is Conceivability a Guide to Possibility?” Philosophy and
Phenomenological Research. Vol LIII, No. 1, pp.1-42.
Van Inwagen, Peter. (1998) “Modal Epistemology.” Philosophical Studies. 92, pp. 67-84.
Zimmerman, Dean. (2000) "Shoemaker’s Argument for his Theory of Properties”, Facta
Philosophica, Vol. 2, pp. 271-290
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