The Republic - a provisional account of the soul (psuche) : complex or simple
One point useful to note is that provisionality hangs over the Republic. The Sun, Line and Cave, for example, are similes or analogies in place of what Plato aka Socrates would prefer, if only he were able, to specify exactly. Just the same provisionality informs the account of the soul. For all that Plato says about justice as the correct relationship between the parts of the soul, in Rep.X.612a he is uncertain of the soul's true nature - whether it is complex or simple (poluides ... monoeides) If simple it has no parts that can stand in a correct relationship. Moreover, it is not even entirely clear what the term 'parts' (mere) denotes if parts exist.
Social mobility
Plato takes it as a brute fact that human beings differ in the preponderance in their souls (psuchai) of reason (logistikon), courage and emotional vigour (thumetikon), and susceptibility to appetite and pleasure (epithumetikon). , Those in whom reason predominates are the philosophers or guardians; those dominated by courage and emotional vigour are the auxiliaries who guard the polis or city as soldiers; and finally, those who live under the sway of appetite and pleasure are the commercial and labouring class.
Plato believes that on the whole sexual unions between the philosophers/ guardians will produce offspring in whom reason predominates as it does in their parents. But there is no iron law here, only a strong tendency. Plato is completely open to the possibility that potential philosophers/ guardians can emerge from outside the philosopher/ guardian class.
This is clear from the Myth of the Metals (Rep. III.415ff). In the language of the myth, the philosophers/ guardians are the class of gold; the auxiliaries, the class of silver; and the rest of the population, the class of iron or bronze. Let Plato speak for himself:
Most of the time you will father children of the same type as yourselves, but because you are all related, occasionally a silver child may be born from a golden parent, or a golden child from a silver parent, and likewise any type from any other type (Rep.III.415b; Plato, The Republic, tr. T. Griffith, Cambridge: CUP, 2000: 108).
When this happens, social mobility is activated to ensure that every child is 'given the position in society his (sic) nature deserves' (415c, Griffith: 108) - up or down. A philosopher/ guardian child can be born to iron or bronze parents and will be removed from her or his environment and educated to their full, elevated potential.
The soul and immortality
Our human nature belongs to us not only when we are alive in the present world but also post-mortem. But what is the post-mortem state or condition of the soul ? Are all parts of the tripartite soul immortal or only the rational part ? The Myth of Er does not offer decisive evidence either way (Rep.X).
Intrinsic psychology
At various places in the Republic Plato endorses the notion that we seek what is best for us, that virtue is best for us, and that virtue requires moral knowledge grounded in the Forms. These are non-contingent facts about - features of - human beings and must be taken into account in any sound view of human nature.
Women and men
Plato is widely regarded as the first feminist in the Western philosophical tradition. Whether he is so or not, Plato does differentiate female and male natures. He is not willing to accommodate women and men is precisely the same account.
Plato's proposals about women come at the beginning of Book V,
where Socrates is represented as having to surmount three waves of
opposition. The first wave concerns the admission of women as Guardians;
the second concerns the communal life of the Guardians; the third concerns
the practicability of the ideal state, and this leads into the discussion which occupies the rest of Books V-VII. The figure of separate 'waves' is
constantly brought before us; for Plato the capacity of women to be
Guardians is a separate question from the replacement of nuclear family
life.
Plato begins his treatment of the first problem (451) by extending the
metaphor he has used already. Female watchdogs do just what the male
ones do, except that they are weaker, and their lives are interrupted by
giving birth. By analogy, the same is true of women; though they are
weaker than men and their lives are interrupted by childbirth, they are
otherwise the same, and so should be given the same upbringing and
tasks as men, however distasteful the sight of ugly old women exercising
in the gymnasium may be.
Now this is only metaphor-and in fact it does not pretend to be serious
argument. Plato wants to give us a picture first, perhaps so that we have a
vivid idea of what the arguments are about before they are presented,
perhaps also so that he can meet and deflect mere ridicule right at the start,
before the serious discussion. Still, the initial metaphor is important, for
it continues to influence Plato in the actual argument.
Plato now (453b-c) puts forward what he regards as a serious objection
to the idea of women being Guardians. The opponent is made to say that
it contradicts the principle on which the ideal state is constructed-namely,
that each person is to do his own work, according to his nature (453b5).
As women differ greatly in nature from men, they should surely have
different functions in the city (453b10-11).
Plato dismisses this objection as merely captious. Of course it is true
that different natures should do different things, but it does not follow that
men and women should do different things unless it can be shown that they
have natures that are different in the important respect of affecting their
capacity for the same pursuit. Otherwise it would be like letting bald men,
but not hairy men, be cobblers. Plato now claims that men and women
differ only in their sexual roles: men impregnate, women give birth
(454d-e). The objector fails to show that there is any capacity that is
peculiar to women, and Plato claims to show that there are no civic pursuits
which belong to a woman as such or to a man as such (this is the part of the
argument we shall come back to). Since there are no specific male or female
competences, men and women should follow the same pursuits, and
women who have natures suitable to be Guardians should therefore be
appropriately trained.
This is how Plato deals with the first 'wave'. There are three important
points to be made about his argument. [GT: only the first considered here.]
... there is something very odd about the actual course of the
argument from 455a-d. Plato has established the undeniable point that
while women are different from men in some ways and similar in others,
discussion at that level is sterile; the interesting question is whether the undisputed differences matter when we decide whether women should be able
to hold certain jobs. This is the crucial point not only for Plato but for any
sensible discussion of the topic. But Plato's argument is seriously incomplete.
At 455a9-b2 he poses the question, 'Are there any occupations which
contribute towards the running of the state which only a woman can do?'
Very swiftly he claims to show that there are none. Men are better equipped
both mentally and physically (455b4-c6). So in every pursuit men can do
better than women, though it is not true that all men do better than all
women (455d3-5). Women, he says, are ridiculed when men do such
traditional feminine tasks as cooking and weaving better than they do; still,
it follows from what has been said that if men bothered to turn their
attention to these tasks they would do them better. 'The one sex is, so to
speak, far and away beaten in every field by the other' (455d2-3). (Julia Annas, 'Plato's "Republic" and Feminism', Philosophy, Vol. 51, No. 197 (Jul., 1976), pp. 307-321
: 308-9.)
Something to note here is that Plato does not appear to think that it is for merely cultural or reproductive reasons that women are disadvantaged in certain respects against men. There is presumably a feminine essence or essential differentia by virtue of which 'in every pursuit men can do better than women' but we are given not the slightest indication of the rationale for this (incredible) claim. The inference is unavoidable, however, that Plato believes that to suppose a single human nature, undifferentiated between women and men, is a wrong account of things.