Plato’s Proof of God’s Existence (Book X of The Laws)


In Book X of The Laws, the Athenian provides an argument for the existence of god. Unholy acts are committed by those who suffer from three kinds of misconception, which are that gods do not exist, or they exist but do not care about human affairs, or that they can be bribed with sacrifices (Jirsa 239; Laws Book X 885e). The Athenian believes that the atheist ought to be provided with proof of the existence of gods before any punishment is imposed on them for impiety (885c-e).[1]  The Athenian aims to provide a proof that soul is fundamental (892c-d).[2] The proof that the Athenian provides is an argument from motion (Stalley 169-170). In short, a thing can have one of two properties: (a) the property of moving other things without moving itself, and (b) the property of moving other things as well as itself (894b-c). All motion has an absolute origin, which cannot be type (a), because things of that type can only transmit motions to other things by virtue of themselves being moved by something external to them (894e). To be the originator of motion, a thing must be of type (b), because it must have the potential to originate motion within itself, as there is nothing but itself to transmit motion to other things at the beginning of the sequence of moving things. Things of type (b) are said to be alive, or ensouled (895c). So, the originator of motion is soul, which makes soul more fundamental than physical things (892c-d; 896b-c). Since soul is more fundamental than physical things, the properties of soul are more fundamental than the properties of material things (896c-d). Soul, being fundamental, is the source of everything less fundamental, which includes values like good and bad (896d).

Soul controls the heavens and the earth because they are also in motion (896d-e). The goodness or virtue and rationality of the originator of motion is inferred from the fact that the motion of the heavens is orderly and rational, which means that the originator of that motion must also be virtuous, orderly, and rational (896e-898c). This paper will be structured as follows. In section one, I will explain the doctrine against which the Athenian is arguing. In section two, I will lay out the argument’s premises, and explain the rationale behind them. Finally, in section three, I will assess the validity and soundness of the argument.

  1. Physicalism

The Athenian’s opponent is the physicalist. Physicalism is responsible for the attractiveness of atheism (887b-c). In the context of the Laws, physicalism is the doctrine that all things that come into being do so by virtue of nature, change, or art (888e).[3] The physicalist believes that the basic elements (earth, air, water, and fire) exist by nature, and they combine in various ways by chance to produce everything else that exists (889a). Things that exist by virtue of art are secondary to those that exist by chance or nature (889c). Examples of things that exist by virtue of art are things crafted by humans and human conventions (889c). When it comes to crafts that involve mixing labor with the natural world, the products such as fresh produce and meat are considered natural (Jirsa 242-243). The secondary, or less fundamental (derivative) entities are those that do not involve outright mixing of human labor with the natural world. Statesmanship, for example, seems not to involve the natural world, so it is secondary to the natural by virtue of the object of its inquiry (the state) being a product of art (889c-e). Furthermore, on the physicalist view, the gods are the products of human activity, and therefore are not ontologically primary (889e). Clearly, this threatens the notion that the laws which structure Magnesia are from the gods, so it is important for the Athenian to refute the doctrine of physicalism (886e-888e). So, the Athenian, encouraged by Clinias, sets out to formulate an argument against physicalism, which establishes the existence of god.

  1. The Argument

The Athenian begins his exposition of the argument by laying out a taxonomy of motion, which seems to be ordered according to ontological priority (Jirsa 244). The motion I classified as type (a) is identified with that which can move other things but cannot move itself, and the motion I classified as type (b) is identified with that which can move other things and itself (894b-c). Types (a) and (b) motion are considered to be the most basic kinds of motion in the Athenian’s taxonomy (Jirsa 244). Since the Athenian aims to refute the doctrine of physicalism, which says that earth, air, water, and fire are natural, or fundamental, which is to say that they are ontologically primary, and everything else derives its being from them (Jirsa 243; Laws Book X 889a). So, the Athenian must find the fundamental kind(s) of motion, and he must show that it does not fall within the set of things considered natural (fundamental) by the physicalist.

The Athenian proceeds by showing that type (b) motion is more fundamental than type (a) motion. Since all motion must have an absolute origin, there must be an originator of motion (894e). The originator cannot be of type (a), because it would have no source for its ability to move other things. If there is no prior motion to move the originator, then the motion that the originator transfers to other entities in motion must come from within the originator, which is to say that the originator is of type (b). So, the originator of motion must be self-moving and capable of moving other things. Self-motion, therefore, is the fundamental kind of motion (895b). The first premise of the argument is:

  1. Self-motion is prior to all other motion.[4]

The Athenian bolsters the first premise by considering a thought experiment. If all things in motion stopped moving and were stationary, which would be identifiable as the first motion? Type (b) must be the first, because if it were type (a), it would require a prior transfer of motion to enable the first motion to move other things, which, ex hypothesi, cannot exist (895b).

The Athenian then aims to show that soul is identical to self-motion. When we examine the world around us, those things we consider self-movers are what we classify as alive (895c). Things that are alive are also ensouled (895c). So, self-movers are ensouled, since self-movers are alive, and the set of living things is a proper subset of ensouled things (Jirsa 246). The second premise of the argument is:

  1. Soul is self-motion.[5]

The Athenian backs up the second premise by mentioning that we can see three aspects of something, namely its being, its name, and its definition (895d). The Athenian’s definition for the entities picked out by the name “soul” is just, “that which is self-moving” (895e-896a). So, the thing denoted by the name “soul” is the same thing as is defined as, “that which is self-moving.” So, to say that something has a soul is to say that it is capable of self-motion (Jirsa 246). From premises one and two, the Athenian infers that soul is prior to all other motions and entities that are or could be in motion (Jirsa 253; Laws Book X 896b-c). So, the first conclusion is:

3. Soul is prior to all other motion.[6]

The notion of priority that the Athenian employs seems to be both temporal and ontological (895b). So, soul is temporally and ontologically prior to all other motions, including the motions of the elements that the physicalist posits as fundamental. The Athenian has shown so far that soul is ontologically and temporally prior to the physical, which means that soul, rather than the elements (earth, air, water, and fire) falls in the category of natural that the physicalist employs (892c).

At this point in the argument, the Athenian suggests that it could be two souls that govern the heavens and the earth, one good and the other one bad (896e-897c). The Athenian aims to show that it is a good soul that governs the heavens and the earth, which would entail that the world we presently inhabit is ordered rationally and virtuously.[7] He points out that the products of soul guided by virtue and reason are different than those of soul not guided by reason (897b). The products of soul guided by virtue and reason are better than those produced by a soul not guided by virtue and reason. Because the heavens move in a way that resembles reason, the soul which orders the heavens must be guided by virtue and reason. But if the heavens were ordered by an irrational soul, the motions of the heavenly bodies would not be as they actually are (897b-898b). From this we get the next steps in the Athenian’s argument:

  1. If the heavens move rationally and virtuously, then soul guided by virtue and reason orders the heavens.
  2. The heavens move rationally and virtuously.[8]
  3. Soul guided by virtue and reason orders the heavens.

The second conclusion of the Athenian’s argument, then, is that the heavens are ordered by a rational and virtuous soul, because to be guided in action by virtue and reason is to be virtuous and rational. Finally, to get to god, the Athenian points out that the soul guiding the sun must be regarded by anybody as a god (899a). Since the other heavenly bodies move in ways resembling the sun in relevant respects, it follows that the souls guiding those bodies must also be regarded as gods (899b-c).

Now, to complete his case, the Athenian must show that the gods care about human affairs, and are not capable of being bribed. Since the gods are all powerful, all knowing, and all good, they cannot disregard human affairs, because doing so would call into question their power, knowledge, and goodness (901d-e). For the gods to disregard human affairs would be for them to succumb to indolence and idleness, but given their attributes, they cannot succumb to such things. Furthermore, to take bribes would be to succumb to self-indulgence, which would call their goodness into question (901e). So, the gods concern themselves with human affairs and are not susceptible to bribery.

  1. Evaluation

The Athenian’s argument seems valid. The first conclusion (3) follows from the first two premises (1 & 2) by virtue of substituting co-referring expressions (soul and self-motion). The second conclusion (6) follows from premises four and five by modus ponens. Finally, the Athenian’s conclusion that the gods concern themselves with human affairs and cannot be bribed follows from the properties he ascribes to the gods. If those properties logically exclude disregarding human affairs and being bribed, then it is a valid form of argument to move from some set of properties being possessed by some entities to the negation of the proposition that the properties logically excluded by that set are possessed by those same entities.

The Athenian’s argument is quite ingenious, but it is susceptible to various criticisms which call its soundness into question. First, the notion of ontological priority employed by the Athenian to justify his first premise can be questioned. If one embraces the (contemporary) orthodox way of doing ontology, the notion of levels of being will become unintelligible. It is only given the idea that some things are more fundamental than others such that they form more basic levels of being that the justification given for the first premise can work. Second, the reasons given to think that there must be a first motion were insufficient. Merely thinking of a hypothetical situation in which motion is stopped, and we are free to judge which motions are more fundamental than others is not enough to justify the claim that there was a first motion. The defender of the view that there is an infinite series of motion-transference that stretches backwards eternally will not see that, given a stoppage of all motion, there must be a first motion. Furthermore, Parmenides doubted the reality of motion (Stalley 170).

The fourth and fifth premises of the Athenian’s argument are also questionable. Setting aside anachronistic reasons such as the falsity of the Athenian’s thesis that the heavenly bodies move in perfectly circular orbits, there are still other reasons to doubt his premises. First, premise four is a conditional, and it seems not to be true. There are possible states of affairs where the heavenly bodies happen to move in virtuous and rational ways merely by virtue of chance, or by virtue of the nature of the elements composing them. In other words, the physicalist thesis examined in section one seems to have the resources to account for the appearance of the virtuous and rational guidance of the heavens. Perhaps the intrinsic properties of each kind of element constrains the range of possible combinations of those elements, and the possible motions of those composite objects such that they inevitably would move in apparently virtuous and rational ways. The Athenian does not address this possibility at all. So, on the physicalist view, the fourth premise is questionable because the consequent of the conditional has not been shown to be a consequence of the antecedent obtaining.

Finally, moving from the claim that the soul which guides the heavens is rational and virtuous to the claim that that soul is all powerful, all good, and all knowing seems to be a non sequitur.[9] The soul which guides the heavens may be only capable of moving the heavens and nothing else, perhaps by virtue of a limitation on its power, or on its knowledge. Maybe all such a soul can do is move the heavenly bodies in a circular fashion, forever. That soul could not concern itself with human affairs, because it would be outside of the scope of its power or knowledge to do so. Even if we grant the Athenian’s claim that the soul has the properties of maximal power, knowledge, and goodness, it may not follow that the soul could not be bribed. It could be the case that we humans are so limited in our moral knowledge, that the soul could allow the wicked to prosper by bribing it with sacrifices because doing so allows for some greater good which we cannot currently comprehend. So, even granting the set of properties that the Athenian ascribes to the soul he calls god, it does not obviously follow that that set logically excludes the ability to be bribed.


I have examined the argument in Book X of The Laws presented by the Athenian. The argument’s premises are all questionable, which means that it is within the physicalist’s rational rights to doubt the conclusions. The Athenian aimed to provide reasons to believe in gods which would be provided to atheists before punishing them for impiety (885c-e). The gods, given the Athenian’s argument, concern themselves with human affairs and cannot be bribed. They are not fictions created by humans, as the physicalist maintains (889e). However, the Athenian underestimates the resources available to the physicalist. The physicalist can resist the Athenian’s argument while remaining within her own ontological framework. So, the Athenian has failed to supply the atheist with reasons to believe in gods.


[1] Whether or not the proof is supposed to be rationally compelling or just sufficient for rational acceptance is an open interpretive question (Jirsa 241).

[2] Plato seems to use the term “natural” in the same way as “fundamental” is used by Jonathan Schaffer, which is to denote ontological priority (Chalmers 2009; Jirsa 243).

[3] I am using “physicalism” to characterize the Athenian’s opponent because his opponent holds to the view that the elements (earth, air, water, and fire) are fundamental or primary, and those elements seem paradigmatically physical entities (Jirsa 2008).

[4] See (Jirsa 253).

[5] See (Ibid 253).

[6] See (Ibid 253).

[7] By virtue of being ordered by a rational and virtuous soul.

[8] See (Book VII 822a-b) for a description of the moon, sun, and stars following a circular path, and compare with what is said at (Book X 897d-898b). Both the moon, sun, and stars and the image chosen to represent reason are circular (Jirsa 252). So, the motions of the heavenly bodies and of reason are the same.

[9] I am using the singular instead of “souls” for stylistic purposes. The Athenian’s argument actually entails that there are multiple souls that are virtuous and rational. But this does not affect my criticisms.

Works Cited

Chalmers, David John, David Manley, and Ryan Wasserman. “On What Grounds What.” Metametaphysics: New Essays on the Foundations of Ontology. Oxford: Clarendon, 2009. 347-83. Print.

Jirsa, Jakub (2008). Plato on characteristics of god: Laws X. 887c5-899d3. Rhizai. A Journal for Ancient Philosophy and Science 5:265-285.

Plato, Malcolm Schofield, and Tom Griffith. Plato the Laws. Cambridge: Cambridge UP, 2016. Print.

Stalley, R. F., and Plato. An Introduction to Plato’s Laws. Indianapolis, IN: Hackett, 1983. Print.