At 133b4-c1 Parmenides told Socrates that the greatest problem concerning the Forms is the question of how can they be known ‘if they are such as we maintain they must be (onta toiauta hoia phamen dein einai ta eidê, 133b4-6)’. Socrates asked: ‘In what way (Pêi dê, 133c2)’? Parmenides replied: ‘Because (Hoti), I think that you and anyone else (oimai an kai se kai allon) who maintains a being of each thing existing as something alone by itself (hostis autên tina kath’ hautên hekastou ousian tithetaI einai) would in the first place agree that none of them exists in us (homologêsai an prȏton men mêdemian autȏn einai en hêmin).’ Socrates agrees: ‘For how could it still be alone by itself (Pȏs gar an autê kath’ hautên eti eiê)?’ Parmenides appreciates Socrates’ reply, ‘Well said’ (Kalȏs legeis).
It is noteworthy that until this point the ontological status of the Forms proposed by Socrates remained uncertain. At 128e6-129a1 Socrates asked Zeno ‘do you not acknowledge that there is a Form of likeness alone by itself’, and Parmenides opened his questioning of Socrates’ theory by asking ‘Do you think (dokei soi), as you say (hȏs phêis), that there are certain Forms (einai eidê atta) by partaking of which these other things have got their names (hȏn tade ta alla metalambanonta tas epȏnumias autȏn ischein, 130e5-6)’. Socrates’ ‘Certainly’ (Panu ge, 131a3) does not prevent him from suggesting that each of the Forms (tȏn eidȏn hekaston) may be just a thought (noêma), to which it would appertain to be nowhere else (kai oudamou autȏi prosêkêi engignestai allothi) than in souls (ê en psuchais, 132b3-6).
It is at this junction that the gap between the historical Socrates and Plato looms large. Socrates in his youth considered the Forms, Parmenides showed to him the difficulties the theory involved, and left him in the state of philosophic ignorance. Socrates stayed in that ignorance until his last day. Initially, on that day, he hoped to establish the immortality of the soul on the basis of how viewed the Forms in his ignorance, that is as they are present in our souls:
‘If the objects we’re always harping on exist (ei men estin ha thruloumen aei), a beautiful, and a good and all such Being (kalon te ti kai agathon kai pasa hê toiautê ousia), and if we refer all things from our sense-perceptions to that Being (kai epi tautên ta ek tȏn aisthêseȏn panta anapheromen), which existed before our birth (huparchousan proteron), finding it to be ours (aneuriskontes hêmeteran ousan), and if we compare these things with our soul (kai tauta ekeinêi apeikazomen), then just as surely as those objects exist (anankaion, houtȏs hȏsper kai tauta estin), so also must our soul exist (houtȏs kai tên hêmeteran psuchên einai) before we were born (kai prin gegonenai hêmas) … Is this the position (ar’ houtȏs echei)? Is it equally necessary that those objects exist (kai isê anankê tauta te einai), and that our souls existed before birth (kai tas hêmeteras psuchas prin kai hêmas gegonenai), and if the former don’t exist (kai ei mê tauta), then neither did the latter (oude tade)?’ – ‘It’s abundantly clear to me, Socrates,’ said Simmias, ‘that there’s the same necessity in either case (Huperphuȏs, ȏ Sȏkrates, ephê ho Simmias, dokei moi hê autê anankê einai).’ (Phaedo, 76d7-e10, tr. David Gallop, with some changes)
It was only after Cebes pointed out that the pre-existence of the soul does not guarantee its existence after our death, that Socrates was compelled to view the Forms as independent causal agents existing apart from our souls. Socrates recapitulated Cebes’ arguments as follows:
‘You want it proved that our soul is imperishable ad immortal … As for showing that the soul is something strong and god-like, and existed even before we were born as men’ this does not preclude the possibility that the soul’s ‘very entry into a human body was the beginning of its perishing, like an illness.’ Cebes agreed: ‘Those are my very points.’ (Phaedo 95b9-d2) – Phaedo: ‘Here Socrates paused for a long time examining something in his own mind. He then said: ‘It’s no trivial matter, this quest of yours, Cebes: it calls for a thorough inquiry into the whole question of the reason for coming-to-be and destruction. So I will, if you like, relate my own experiences on these matters … When I was young, Cebes, I was remarkably keen on the kind of wisdom known as natural science; it seemed to me splendid to know the reason for each thing, why each thing comes to be, why it perishes, and why it exists.’ (Phaedo 95e7-96a10)
After describing his disenchantment with natural science, Socrates describes the state of mind in which he embraced the Forms in his state of philosophic ignorance: ‘Then I no longer understand nor can I recognize those other wise reasons; but if anyone gives me as the reason why a given thing is beautiful either its having a blooming colour, or its shape, or something else like that, I dismiss those other things – because all those other confuse me – but in a plain (haplȏs), artless (atechnȏs), and possibly simple-minded way (kai isȏs euêthȏs), I hold this close to myself: nothing else makes it beautiful except that beautiful itself, whether by its presence or communion or whatever the manner and nature of the relation may be, as I don’t go so far as to affirm that, but only that it is by the beautiful that all beautiful things are beautiful. Because that seems to be the safest answer to give both to myself and to another (touto gar moi dokei asphalestaton einai kai emautȏi apokrinesthai kai allȏi), and if I hang on to this (kai toutou echomenos), I believe I’ll never fall (ouk an pote pesein).’ (Phd. 100c9-d8, tr. D. Gallop)
It is only on the basis of further reflecting on this view of the Forms as they simply exist in our souls, which as such is safe, that Socrates believes to have found a new safe way – ‘from what’s now being said I see a different kind of safeness beyond the answer I gave initially, the old safe one (legȏ dê par hên to prȏton elegon apokrisin, tên asphalê ekeinên, ek tȏn nun legomenȏn allên horȏn asphaleian, 105b6-8, tr. Gallop)’ – in which he can consider the Forms as causal agents, which as such are inseparable from our souls and thus guarantee our soul’s immortality.
Only on his last day thus Socrates embraced the Forms as Plato had conceived them and immortalised in the Phaedrus (written some five years prior to Socrates’ death, see The Lost Plato on my website), the Forms that Plato does his best to defend in the Parmenides.