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Platonic Causes

DAVID SEDLEY

ABSTRACTThis paper examines Platos ideas on cause-effect relations in the Phaedo . It maintains that he sees causes as things (not events, states of affairs or the like),

with any information as to how that thing brings about the effect relegated to astrictly secondary status. This is argued to make good sense, so long as we recog-nise that aition means the thing responsible and exploit legal analogies in order to understand what this amounts to. Furthermore, provided that we do not pre-suppose that we already know what can and what cannot count as a cause, Platoproves to have an attractive case for his principle that all causation is a matter of like causing like. Once we appreciate this, we are a little closer to understand-ing his more idiosyncratic principle, which although puzzling is ubiquitous in his

writings and often invoked as a premise in key arguments, that opposites cannot cause opposites.

The last part of the paper turns to formal causes, defending Platos advocacy

of them, and examining their role in the Parmenides Third Man Argument. Themain proposal is that Platos conception of Forms as causes opens the door to abetter version of that arguments Non-identity premise than those currentlyavailable.

I. What is a cause?

The nal argument of Platos Phaedo seeks to show that such is thesouls causal role as the bringer of life to the body that it itself must beessentially alive; therefore on the approach of the opposite property, death,it is unable to perish, and must instead take the only alternative option,to withdraw. In order to prepare the ground for this argument, Socratesrecounts his own intellectual progress with regard to the correct under-standing of causation (96a-102a). In his youth, he explains, his search for the causes of things led him to consider all sorts of unsuitable candidates

for this role, items which did not on re ection turn out to be properly cor-related to the effects they were postulated to explain. Nor was he, as he


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Socrates retreated to his Second Voyage, his reliance on the hypothesisthat each property of a thing is caused by the appropriate Form: F thingsare (or become) F because of the F. However, later on (105b-c) he seemsto allow a more subtle kind of cause, namely that F things should bemade F by the presence of something which essentially brings the FormF-ness with it, in the way that re, being essentially hot, by its presencein things makes them hot.

Plato favours the following range of locutions to express what appearsto be his notion of cause:

(1) ation / ata: cause/causation1

(2) di + accusative, or causal dative: because of(3) poien= to cause (to), to make (F) (99b7, 100d5)

These, leaving aside syntactic differences, are to all appearances usedinterchangeably throughout, and there is every reason to conclude that they combine to represent for Plato a unitary notion of cause. He isready to consider a variety of competing claimants to the descriptioncause, admitting only some of them as satisfying all the relevant crite-

ria. But those criteria, regarding what in principle may or may not count as a cause, do no themselves appear to shift.

The adjective atiowfollowed by a genitive means responsible for. Togive the cause ( ation) of x is to point to the thing responsible (t ation)for x, and thereby to assign to that thing the responsibility ( ata) for x much in the way that a lawcourt seeks to determine the person respon-sible for a crime, or to attribute the responsibility. When I say the thing

responsible, my word thing is deliberately vague. Plato does not in thiscontext show the slightest interest in distinguishing between metaphysi-cally different kinds of thing: the thing considered as a candidate for thecause of some effect can just as well be a physical stuff like re or bone,a mathematical process like addition, the good, a soul, intelligence, or aForm such as Largeness or Oddness. What determines the success or fail-ure of the candidate cause is nothing to do with its metaphysical status, 2

but purely, as we shall see, its logical or quasi-logical relation to the effect.


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Standardly, it is the thing itself, rather than some fact or event involv-ing it, that Plato nominates as cause, much as in a legal context a person,rather than an event involving that person, is ultimately nominated as re-sponsible for, or guilty of ( atiow), the crime. Occasionally in this passageof the Phaedo , however, what is nominated as the cause is not a simplething but a complex process, event or fact involving it. This complexdescription, it turns out, can be used interchangeably with a simple ref-erence to the thing which features in it (96e2-4, cf. 101b4-7; 98d-99a;100d3-8). For example, if 10 is greater than 8 because of 2 having beenadded to it, that turns out to be equivalent to saying that 10 is greater than 8 by 2 or because of 2 (causal dative).

Which of these two is meant to be the more precise formulation of thecause? It is often assumed that the fuller formulation must be the morecorrect, but there seems to me to be strong evidence against any such pre-sumption. At 100d3-e3 Socrates rst uses this fuller type of formulation

what makes things beautiful is, he hypothesises, the presence or sharing(or whatever it may be) of the Form of Beautiful. However, he then de-clines to specify the nature of that Form-particular relationship (for I

dont go so far as to insist on that: o gr ti toto diisxurzomai, d6-7),and instead strips the causal statement down to what he declares to beits completely safe kernel: It is because of [causal dative] the beautifulthat all beautiful things are beautiful. 3 I read this as strong evidence that the essence of a causal statement lies in its nominating the item whichfunctions as the cause, and that any further statement about how theitem achieves its effect is secondary. This again invites a legal analogy:

ultimately the jury must decide that you were responsible ( atiow) forthe murder; how you brought it about strangulation, starvation, poison-ing etc. is secondary when it comes to the apportionment of guilt orresponsibility.

Platos pared down causal statement here, It is because of the F that F things are F, claims to be utterly safe infallible. Frequently in his

I can nd no common ground at all: G. Vlastos, Reasons and causes in the Phaedo ,Philos Rev 78 (1969) 291-325 repr in his Platonic Studies (Princeton 1973)


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dialogues propositions with this form are treated as self-evident truths: for example, that it is because of wisdom that the wise are wise, because of temperance that the temperate are temperate. 4 Moreover, Plato is by nomeans alone in treating causation along these lines. What is essentiallythe same principle that like causes like can be traced back to Anaxagoras(B10), and forward to Aristotle (especially Metaphysics Z 9) 5 and Hellen-istic debate.

Conversely, and more idiosyncratically, Plato often treats as self-evidently impossible statements to the effect that it is because of theun-F that F things are F, where un-F is, in some sense recognised byPlato, the opposite of F. The language used to express such an impossi-bility is both strong and explicit. Here are some prominent examples:

Phd. 68d: that someone should be brave because of cowardice isirrational or illogical ( logon).

Phd. 68e: that people should be temperate because of intemperanceis impossible ( dnaton).

Phd. 100a-b: that someone should be large because of somethingsmall is weird ( traw).

Parmenides 131c-d: it will be illogical ( logon) if Forms are dividedup, so that what causes large things to be large is a relatively smallpart of Largeness.

Republic I 335c-d: that musicians should because of their music makepeople unmusical, or the just because of their justice make peopleunjust, is impossible ( dnaton).

Protagoras 355d: that people should do what is bad because they areovercome by what is good is ridiculous ( geloon). (That the talk of being overcome by something states the cause of the behaviour inquestion has been made explicit back at 352d8, ation, and 353a1,di tata.)Theaetetus 199d: that knowledge should cause ignorance, ignorancecause knowledge, or blindness cause seeing is a great illogicality(poll loga).

It seems abundantly clear that Plato sees some causal relationships, of the


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with the self-evident truth of tautologies and the self-evident falsity of self-contradictions. The question is, what is it about his view of causethat makes these matters so self-evident?

First, it is worth remarking that his abhorrence at opposites causingopposites somehow re ects a broader abhorrence at the idea that one of a pair of opposites might in any way characterise the other. According tothe Phaedo (102b-103c), a pair of opposites like small and large may co-exist in the same object, taking it in turns to advance and retreataccording to the relation in which the object is currently being viewed,and one of them will succeed the other in a process of change like growth.But, emphatically, they will never dare to be characterised by each other:the large in you will never become small. In the Parmenides (129b-e)Socrates urges at length and in the strongest possible terms that, while anyparticular may unproblematically participate in both of a pair of opposites,it would be bizarre ( traw), amazing etc. if Likeness itself were unlike,if One itself were many, and in general if the actual genera and speciesdisplayed their opposites within themselves, undergoing these oppositesas affections (129c). Yet again in the Sophist (252d), that motion should

be at rest or rest be in motion is by the greatest necessities impossible(taw megstaiw ngkaiw dnaton). Or, to take an adverbial version of thesame abhorrence, in the Theaetetus (189c-d; cf. Rep. 382a4-5) Socrates is

worried by the description of something as truly false, which he com-pares to slowly quick, heavily light or any other opposite comingabout not in accordance with its own nature but in the opposite way to it-self, in accordance with the nature of its own opposite. Still in the Sophist

it is quite bizarre ( mla topon) according to the sophist (240b-c), anddaring according to the Eleatic Stranger (258d), to a f rm that there isntvw t m n, and arguably the daring statement only proves acceptableto the latter because he has decided in the end that being and not-beingare not true opposites. 6

Just how intimate the link is between these various kinds of logicallyabhorrent interaction between opposites is not a simple question to

answer. But there is some reason to think that Plato would see the adver-bial cases, F-ly un-F, as virtually interchangeable with the causal cases,


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argues for a straight equivalence between somethings being done F-ly andits being done out of F-ness (causal dative), for instance that what isdone foolishly is what is done out of folly. So the puzzlement over slowlyquick and the like may even be reducible to puzzlement over the causalversion, quick because of slowness. Alternatively, and more plausibly,both may be reducible to puzzlement as to how quickness could be in any

way characterised by slowness.I am very far from pretending to understand what is going on in these

and similar passages. But I am con dent (a) that the pattern of reasoningI have documented is far too deep-seated in Platos thought to be ex-plained away either as humorous or as his idiosyncratic way of express-ing some harmless truth, and (b) that we will never fully understandPlatos logic and metaphysics until we do understand what is driving himhere. Some of the examples I have listed, such as those at Protagoras355d, Parmenides 131c-d and Theaetetus 199d, provide the basis of cru-cial refutations within Platonic arguments, and it is a pity that moderncommentators have failed to recognise that this strange but ubiquitousPlatonic causal principle is at work in them.

As a step towards understanding why Plato is so ercely attached tothe principle that opposites cannot cause opposites, the most that I canhope to achieve in this paper is an improved grasp of its positive counter-part, the principle that what causes F must itself be F.

First we must take a glance at the kind of causes that Socrates con-siders acceptable, and the kind he considers spurious, in the autobiographi-cal passage of the Phaedo . The following chart lists the main examples he

discusses there, adding in square brackets a number of guesses as to howhe might complete the picture. (For the laws cited here, see p. 121)

Causation at Phd. 96a-101c (+ 105b-c)

( rst voyage) (second voyage) (105b-c)effect spurious cause objection intelligent cause safe cause subtle

cause

(a) a human be- eating, or adding [these also [part of [largeness]ings growth esh to esh bring about providentially


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(cont. Causation at Phd. 96a-101c (+ 105b-c) )

( rst voyage) (second voyage) (105b-c)effect spurious cause objection intelligent cause safe cause subtle

cause

(c) 10 being more 2 [2 also ? numerousnessthan 8 (96e2-3) makes 8 (101b4-6)(96e1-3) less (Law 3)]

(d) 1 becoming 2 addition (97a1) theyd be ? twoness(96e7-9, or division opposite causes (101c2-7)97a5-7) (97a7) of the same

effect (Law 2)(97a7-b3)

(e) shape and air, aether, [these could to give it ?position of water (Anaxa- result in any stabilitythe earth goras) (98c1) shape/arrange- (108e-109a)(97d5-98a2) ment? (Law 3)] cf. (g)

(f ) celestial aether (Anaxa- [aether could just [to communi- ?motions (96b9, goras) (98c1) as easily produce cate number98a2-b2) the opposite etc.? ( Timaeus

motions (Law 3)] 39b, 46e-47c,90c-d)]

(g) the earths a vortex [a vortex also part ofstability (Empedocles) brings about the overall [rest?](99b6-8) or a cushion motion; air also good cosmic

of air (Anaxa- lets things fall arrangementgoras) (99b6-8) (Law 3)] (99c5-6)

(h) Socrates sit- bones and bones and sinews the Athenians [sitting?]ting in prison sinews (98c4-d6) are just as and Socrates(98c2-4) effective for judgements

running away about what is(Law 3) best (98e1-5)(98e5-99a4)

(i) thought/wisdom blood (Empe- [these things can wisdom ? soul( phronein ) docles), air have the opposite ( phronesis ) is(96b3ff.) (Anaximines), effect, e.g. in a intrinsically

re (Heraclitus), corpse (Law 3)] good (69a-b)brain (Alcma-eon?) (96b3ff.)

(j) a things being its colour, or [same colour/ [by (human or the beautifulbeautifu l shape (100d1-3) shape can make divine) design] (100d3-e3)(100c10-d1) a thing ugly

(Law 3)]


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as effective at making it cold in winter. An intelligent cause, if we couldnd one to place in column 4, would be cosmic nous , which orders every-

thing, including summer heat, for the best. Next, the safe cause wouldbe, quite simply hotness. And if nally a subtle cause were to besought, it would have to be the re travelling from the sun, which isinalienably hot and therefore necessarily brings heat with it.

As has often been remarked, at least the following three Laws of Causa-tion are being assumed by Plato:

If x causes anything to be F (whose opposite is un-F)(1) x must not be un-F

(2) xs opposite must not cause anything to be F(3) x must never cause anything to be un-F

Plato, I have argued, regards as the cause of a given effect whatever thingin the story it is most appropriate to attach the blame to. How does Platodecide which item quali es for this? Commentators have often enoughsuccumbed to the temptation to frame their answer in terms of necessaryor su f cient conditions, but it seems to me that this cannot do justice

to Platos approach. Socrates having bones and sinews is said to be anecessary condition of his sitting in prison, but explicitly not the cause.Conversely, Socrates decision that it is best to stay and face the deathpenalty is explicitly the cause of his sitting in prison, but cannot be asu f cient condition of his doing so or his bones and sinews could notbe said, as they are, to constitute a further necessary condition. These con-siderations at least show that Platonic causes are not straightforwardly

identi able with either necessary or su f cient conditions. But there is afar more fundamental consideration to add, one which shows that theycannot be conditions at all. If causes are essentially things , and theseinclude simple things like the beautiful and intelligence (as distinct from states of affairs, events etc.), talk of necessary or su f cient conditionsbecomes unsatisfactory, since no causal theory could coherently describesuch a thing , as distinct from some fact about the thing like its presence

on the scene, as constituting any kind of condition. Your stabbing methrough the heart may be a su f cient condition of my death, but it is


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the dominant notion motivating Plato that he is requiring a descriptionunder which the cause in question will prove maximally explanatory of its effect, in the way that to adapt an example from Aristotle it ismore explanatory (though it may be no truer) to call the person respon-sible for my house a builder than an amateur trombonist. But that thiskind of explanatoriness is not what he is seeking seems clear to me. In nocase does Socrates replace a rejected cause, such as the bones and sinewsrejected as the cause of his sitting, with a redescription of the same item.Rather, he each time substitutes a reference to a quite different item, inthis case Socrates judgement about what is best. Socrates anyway assumesthat a satisfactory cause must be able to survive such redescription, at least in the following case: he excludes a head as the cause of someones large-ness on the ground that, a head being something small, this causal account

would entail something smalls being the cause of largeness (101a-b). It seems, then, that causal contexts are referentially transparent, and the aimof causal inquiry is to identify the thing responsible, no matter under what description.

Of course it can hardly be denied that nding the cause of somethingmay often play a crucial part in explaining it. My warning is against tak-ing Platonic causes to have a primarily epistemological function of thekind outlined above. If I am right, they constitute less an epistemologicalthan an ontological category. Platos approach is to sift through the itemsthat play a part in the story, and to ask which among them has some char-acteristic which made it all along such as to bring about the effect in ques-tion. Bones and sinews (see (h) in the chart) were clearly not all along

such as to bring about the effect of sitting in prison, because they are just as suited to the (presumably) opposite activity of running away fromprison (98e5-99a4). A cushion of air (see (g) in the chart) is, likewise, not such as to bring about the effect of the earths stability (as Anaxagorasand others thought), because, we may take Socrates to mean, there is noth-ing about air as such to make it more suitable for holding things up thanfor doing the opposite, letting them fall. These are applications of Law 3.

Similarly (see (d) in the chart), on Law 2, if I am holding one piece of wood and pick up another, addition cannot be named as the cause of my


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the doubling on this occasion, but it does not follow that it is its natureto produce 2, when its (supposed) opposite, division, is just as effectiveat producing the same result: I could simply have broken the rst pieceof wood in two. That is, re ection about its opposite reveals that therecannot be anything about addition as such that links it to the effect inquestion.

If, then, Plato is looking for something which was all along such as toproduce the effect F-ness, it may be hard for him to see what it could ever be about the thing that pointed towards that outcome, if not the thingsbeing itself in its own nature F. At least, it is not hard to illustrate sucha principle, provided that you select your examples carefully. To takePlatos own paradigmatic case from later on in the Phaedo , re by itspresence can only make things hot, never cold, because it is itself bynature hot. Likewise snow, being by nature cold, can by its presence onlymake things cold, and the number three, by being present in a set of things, can only make them odd because it is itself inalienably odd. Theselook like good illustrations of Platos Law 1, that whatever causes some-thing to be F must not itself be un-F, and, equally, of its positive counter-

part, the principle that like causes like. 8It is tempting to react with counterexamples. 9 Must the cause of some-

ones death be itself dead? Will a court convict you of my murder onlyif you were yourself dead at the time I died? Obviously not, but a Platonictheory of causation might still survive the challenge, so long as it speci escarefully exactly what item is causing what. The jury, in deciding that youare guilty ( atiow) of my death, may strictly speaking mean that you are a

murderous person who can therefore be held responsible for, or the causeof, the murderous act a causal analysis which does appear to obeyPlatonic principles. As for my death itself, well, perhaps the murderousact is not strictly its cause. Perhaps it has no cause at all, beyond a safeformal cause, the onset of death and the concurrent departure of the soul,taking life with it.

This approach is sometimes known as the transmission theory of cau-

sation. In a case like that of heat the name makes easy sense: you canbe made hot only by a hot thing, because nothing else has heat to trans-


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same law, when in the Meno Socrates apologises for his numbing effect on his interlocutor by remarking It is because I myself above all amat a loss that I cause others too to be at a loss. 10 It is easy to think of Socratic dialectic as the device by which he transmits his puzzlement toothers. Even in the simple case where a murderous act is attributable toa murderous person, while there is no use for a causal stage in which themurderousness is transmitted from the agent to the act, as if the act werealready there awaiting the conferment of this property, we might still say,more loosely, that decision-making is the process by which you transmit

your character to your behaviour. But we must be careful. To insist toostrongly on transmission as a distinct stage in the causal process threatensto dilute the immediacy and transparency of the cause-effect relation.When we have accounted for the murderous act by pointing to the mur-derous person, we have already said all that there is to say about wherethe actual responsibility lies. That is why, as we saw earlier, Plato doesnot include in the irreducible kernel of a causal statement the process by

which the cause acts. How the murderousness was transmitted is no moreimportant to a causal account than it was at Phaedo 100d3-e3 to estab-

lish whether it is by sharing, presence or whatever that the Beautifulcomes to make things beautiful.

There is nothing altogether absurd in the prospect of learning to reformour causal language so as obey Platos strictures. And if he can persuadeus that all genuine causal relations have this transparency and immediacy,

why should we object? It may even help us to see why, in cases of acciden-tal killing, we should not hold the unfortunate perpetrator responsible

at all: there is simply no properly causal link between the agents char-acter and the act, in the way that there is when someone elses murderouscharacter becomes the cause of a murderous act.

An apparent further attraction of adhering to so strict a notion of causeis the prospect of circumventing the danger, highlighted by Hume, thatso-called causal relations will prove to be nothing more than regular con-

junctions. One central thrust of Platos account is that reference to mere

situational correlations, like that of air and aether with the earths origi-nal formation, or that of Socrates bones and sinews with his sitting, is a


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endorses is the actual nature of the causing conceptually self-evident.Quite apart from the Humean question, a Platonic approach promises

to save us from the sheer arbitrariness or subjectivity which the task of singling out a cause regularly seems to import. What caused my death?Was it you? Was it your action? Was it your gun, or your ring your gun?Or was it the rupture of my heart, as a forensic scientist is more likely toclaim? Or again, was it reckless provocation on my part, your deprivedchildhood, your callous pursuit of your own ends, the in uence of televi-sion, or any of a thousand other items which various sectional interestsmay choose to privilege as the cause? Platonic causation eliminates allthese impostors at a stroke. 11

It is inadequate, then, to object on the ground that Platos causal the-ory cannot account for all the relations which we consider causal. Maybe,after all, they are not genuinely causal. But can it, at least, deal adequately

with all the cases that he himself considers causal? What about Socratesown expressed ideal of teleological causation? In the passage about thecauses of his sitting in prison, he is rejecting material causes in favourof intelligent, goal-directed causes: the primary reason for his sitting

in prison is his judgement that it is better for him not to escape. Headds that he would dearly love to learn how to establish similar causesfor the arrangement of the cosmos, showing how a divine Intelligence(nous ) ordered it as it is because it judged that this was the best way for things to be.

Since Socrates confesses that he has been unable to discover an ade-quate account of such causes, we should not expect, from his own infor-

mal sketch of the idea, to learn much about how they might be coherentlyformulated. Plato is acknowledging that cosmology was not a disciplineto which his master made any direct contribution. But it is equally clear that Plato himself 12 regards teleological cosmology as a proper philo-sophical project. How, then, does he himself envisage this kind of cause?How, in particular, can intelligent or teleological causes even obey Platosown austere causal principles? For example, if Intelligence is the cause of

11 I am grateful to Christopher Shields for impressing on me the point made in this


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everything, then isnt it (in de ance of Causal Law 3) the cause of oppo-site effects both heat in summer and cold in winter, both light in theday and darkness at night?

I dont think so. If Plato wants Intelligence to be the cause of all things,that will mean all good things. Intelligence is intrinsically good, thereforein so far as it acts upon things it can only make them good. As Socratesemphasises (98a-b), to attribute something to the agency of an intelligence

just is to say why it is best that it should be the way it is. This is in fact a causal thesis almost explicitly maintained in book II of the Republic(379b-c), where Socrates argues that, since god is intrinsically good, heis the cause, not of everything, but only of good things. Intelligence invari-ably aims for the good, and is therefore causally e f cacious only when it succeeds in bringing about a good state of affairs. (If it is wondered whyIntelligence should be absolved of being the cause of its own omissions,failures or mistakes, Platos causal principles again step in with the an-swer. Intelligence, being good and essentially aiming for the good, issimply not causally correlated in the right way to a bad outcome. This islittle more than a development, on a cosmic scale, of the Socratic paradox

that no one does wrong willingly, because intelligence always aims for the good and therefore never intends its bad results.) 13

Thus Platos teleological project is one of investigating, not everythingabout the world, but its goodness. However, the goodness which affects it has enormous causal powers. For example (see (g) in the chart), Socratessays at 99b-c, it is absurd of the natural philosophers to attribute theearths stable position in the cosmos to its resting on, say, a cushion of

air, as if air could compete with the power of the good and the bindingin holding the whole arrangement together. He means, I think, that thegood has this power in virtue of being the goal governing all the activitiesof the divine Intelligence. It is precisely because it is good for the earthto be stable that the divine Intelligence can be relied on to nd a way tomake it so.

Platonic teleology, then, can be read as fully adhering to the strict

Platonic notion of a cause. Teleological causation is from start to nish amatter of the good bringing about the good. It is, in short, a special appli-


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cation of the formal causation to which Socrates turns in his famousSecond Voyage ( Phd. 99c-102a), with its safe causal story that it is the F which causes F things to be F. What it may be thought to antic-ipate in addition is subtle causation of the kind canvassed at 105b-c:intelligence, being intrinsically good, always imports goodness by its pres-ence, just as re, being intrinsically hot, always by its presence makesthings hot.

II. Formal causes

Platos formal causes have received a largely bad press. If you want toknow what makes a sunset beautiful, it may seem quite unhelpful to betold Because of the beautiful. Can these formal causes be other thanvacuous?

They can. There is an enormous value in knowing that the sunset isbeautiful because of the beautiful and not because of, say, its colour. Only

when you know what the genuine cause is do you know what it is that you have to investigate. If you want to understand what makes sunsets

beautiful, dont be sidetracked into investigating the nature of colours.Investigate what the beautiful is in other words, seek to establish theessence of the beautiful by means of a de nition. Likewise, more ambi-tiously, if you want to understand the worlds goodness, forget about air,aether and the like and nd out what goodness is. You will then be ableto trace a causal chain from the nature of the Good, through the inherent goodness of the divine intellect, down to the goodness of the worlds indi-

vidual features. But only someone who grasped the Platonic causal prin-ciples could hope to carry this out.

One di f culty about envisaging this intellectual process is that the Phaedo itself does not explicitly supply working de nitions for any of theForms that it considers, and this has sometimes fostered the impressionthat there is nothing more to formal causal analysis than the utterly trivialundertaking of naming the formal cause: This is F because of F-ness.

However, not only does Socrates indicate, if cryptically, at 101d that theForm that has been posited will eventually need to be de ned, but I am


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least all those present, know what the equal itself is. 15 And when we get tothe account of immanent largeness and smallness at 102a-103a, Socratessounds as if he is in fact assuming as known the de nitions of largenessand smallness later used at Parmenides 150c-d (and perhaps implicit at

Hp.Ma. 294b). Largeness is the capacity to exceed ( dnamiw to perxein),smallness the capacity to be exceeded ( dnamiw to perxesyai); in

which case, equality must presumably be the capacity neither to exceednor be exceeded.

It is, I suspect, because largeness is a Form which we are all expectedto know 16 that Plato repeatedly invokes it to illustrate formal causation.This is true not only in the Phaedo , but also, as I shall now argue, in that classic passage of the Parmenides , the Third Man Argument (132a-b).

I think it is for the following sort of reason that you believe each Form is onething. When it seems to you that there are many particular large things, perhapsit seems to you, as you look onto them all, that there is one Form, the same one,and for this reason you judge the Large to be one.

What you say is true, replied Socrates.But what about the Large itself and the other large things? If you look onto

them all in the same way with your soul, wont a single Large appear again,because of which ( ) all these appear large?

Apparently.In that case another Form of Largeness will put in an appearance, generated

over and above Largeness itself and the things which participate in it. And inaddition to all of these again a further one, because of which ( ) all of them willbe large. And you will no longer have each of the Forms as single, but as in nitein number.

To oversimply somewhat, Parmenides argument runs as follows. A Formis supposed to be that entity in virtue of which a set of things share aproperty: all F things are F in virtue of the single Form, F-ness. This issometimes called the One-over-Many principle. To say that Forms areseparate entails that this Form, F-ness, is something over and above the

Phaedo larger and large are interchangeable cf. 102d-103a for reasons whichthe de nition of large (see immediately below) will make obvious.

15 I therefore agree with Dominic Scott Recollection and Experience (Cambridge


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set of F things. But, given also that the Form F-ness is itself taken to beF Beauty is beautiful, for example positing this Form merely adds onefurther F thing to the list, thus generating a new, expanded set of F things,for which we will have to posit a further Form, F-ness 1. And the same rea-soning will generate a yet further Form, F-ness 2. And so on ad in nitum.

Gregory Vlastos 17 set the terms for modern discusssions of the ThirdMan Argument (TMA) by isolating two controversial premises. Strippeddown, these are:

Self-predication (SP) : F-ness is F Non-identity (NI) : None of the F things is identical with F-ness

Since it has proved hard if not impossible to absolve Plato of beingsomehow committed to SP, 18 and since NI (even when heavily disguised)looks like a direct negation of SP, there must remain a doubt about

whether we have really understood NI. My hope is to show that, provided we keep in sight Platos notion of formal causation, a highly plausibleunderstanding of NI can be found.

It may be helpful to start from a retrospective view of the TMA.

Immediately following it, Socrates retreats to the proposal that Formsare thoughts located exclusively in our souls (132b). He expresses hiscon dence and is not challenged on the point by Parmenides that ifForms were thoughts the Third Man regress would be avoided. Whyso? If Largeness is a thought (call it conceptual Largeness), it is non-identical with the particular largenesses over which it stands. Then what links these particular largenesses and conceptual Largeness itself? Why

wont there be a new thought, conceptual Largeness 1, which links thisnew set of largenesses? On the reasonable assumption that no thoughtcan include itself within its own scope, the thought which is generated bysurveying a set of things which include conceptual Largeness could not itself be conceptual Largeness. And then we would be confronted withthe TMA all over again. Clearly then we must construe either the TMAor the Form-thought equivalence so as to make the latter less vulnerable

to the regress attack.


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I suggest that this requires the following approach. In the TMA, Par-menides generates his second form of Largeness by urging upon Socratesthat he (Socrates) looks with his soul onto the Form plus the particularsthat fall under it and notices what common Form links them all. That is

why Socrates, in the Form-thought passage, responds by explicitly placingthe Form itself within the soul. There it cannot be looked onto by thesoul in the way that the other large things can, and no second Form willbe generated. The One over Many principle was designed to correlate aset of objective items accessed by the mind; if the Form proves instead tobe subjective , it will cease to be one of the items taken in by the survey.We can now see why Plato, in anticipation of this later response, madeParmenides start out in the TMA by emphasising the objective, extra-mental status of Forms. And what better way to substantiate this than bybringing out their objective role as causes : the Form Largeness is actually

what makes large things large. That is a role which it could scarcely per-form if it were a mere human thought.

That the Form has this causal function is in fact explicitly broughtout twice in the TMA by the causal dative, which should be familiar to

readers of the Phaedo as one of Platos standard locutions for a cause,and as the standard locution for a formal cause (as in t kal pnta tkal kal , Phd. 100e, etc.). Indeed, the same causal dative has featuredin Parmenides immediately preceding argument, on the absurdity ofmaking something relatively small viz. a part of Largeness or Equality the cause of a particular things being large or equal (131c-d, cf. abovep. 000 ). It will make a huge difference if we start by noticing this simple

terminological point.19

According to the TMA, the discovery of a Form,Largeness, leads to the addition of Largeness 1, because of which ( )Largeness and the other large things are large; and that in turn likewiseleads to the addition of Largeness 2, because of which Largeness 1 andthe other large things are large.

19 The terminological point has been overlooked by the classic literature on theTMA. However, since I rst wrote the above, the same point has been made byK -C Chang in his 1995 Cambridge Ph D dissertation The role of the Timaeus in


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The attraction of this reading is, I hope, that it offers an immediatelyplausible interpretation of the TMA. If we pay proper attention to thecausal language, we will be well placed to explain how the regress isgenerated.

We still need versions of SP and NI in order to follow the argument.However, SP, the puzzling assumption that e.g. Largeness is large, can for the purposes of the argument be treated as meaning no more than that Largeness, the Form, is itself a largeness, 20 albeit a rather special one. The

whole argument can, for our present convenience, be read as one about the interrelations of a series of largenesses, or cases of largeness, starting

with the individual largenesses (i.e. individual capacities to exceed) of aset of particular objects. My present aim is not to solve the problem of Self-Predication, but temporarily to disarm it in order to concentrate in-stead on the dangers posed by Non-Identity, to which I now turn.

With the help of the causal analysis, we are in a position to rewrite NIas a new, 21 but also I hope entirely credible, premise:

NI *: No cause is identical with its own effect

NI* has many merits. It seems an obvious intuitive truth. It is explicitlystated (with regard to the causes of becoming) as a law at Philebus 27a and

Hippias Major 297c1-2. Above all, it is arguably a principle which Platohad already acknowledged with regard to the causal role of Forms: at

Phaedo 100c he was presumably recognising that F-ness could not be thecause of its own F-ness when he wrote: If anything is beautiful, other than the Beautiful itself , it is beautiful through no other cause than that

it participates in that Beautiful.22

The argument can now run as follows. Take, for convenience, a set of three large things, plus Largeness itself, which stands over them. You nowhave four largenesses the largenesses of the three large things, andLargeness itself. That these are four of a kind, and therefore in need of a

20 Cf. Phd. 102d-e, where our individual capacity to exceed may be called inter-changeably the large in us and the largeness in us.

21 The NI premise thus formulated has much in common with the version offered


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unitary causal account, is con rmed by the fact that they all satisfy thesame de nition which is probably, as we have seen, the capacity toexceed. So what causes them all to be largenesses? Not Largeness itself,since then it would be causing not only other largenesses but also itself,in contravention of NI*. There is therefore a fth Largeness which makesthe rst four largenesses largenesses. But this new Largeness satis es thesame de nition as the other four largenesses, yielding a set of ve large-nesses, for which a yet further cause must be sought. And so on adin nitum.

Looking back on the structure of the argument, we may note that noversion of NI was, or in the context needed to be, invoked as justifyingthe initial separation of Largeness from individual largenesses: that Formsare separate from the things that participate in them was Socrates hypo-thesis, already for some time under active investigation by Parmenides.But as soon as Parmenides came to the second step, and needed an argu-ment for the separation of Largeness 1, it was the causal principle NI*that he reached for.

This might lead us to re ect that NI*, the separation of cause from

effect, would in fact constitute an equally powerful ground for the originalPlatonic separation of the Form Largeness from its effects, such individuallargenesses as yours and mine. Even before he separated the Forms astranscendent entities, Plato was already speaking of them as the causes of their own instantiations (e.g. Euthyphro 6d-e, Meno 72c). Perhaps thenNI* should be added to the motives which we standardly adduce for that single most revolutionary development in Platos metaphysics, his postu-

lation of separated Forms.23

Christs College, Cambridge

23 At the very least, NI* yields Forms which are non-identical with their instances.How Plato gets from this to independently existing Forms (which I take to be intendedby the notion of separation) is a problematic issue (cf G Fine Separation OSAP


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