What philosophers believed marriage is man's ultimate perfection?

Question

It seems Plato believed this when he says, through Aristophanes in the Symposium:

After the division [by Zeus,] the two parts of man, each desiring his other half, came together, and throwing their arms about one another, entwined in mutual embraces, longing to grow into one, they were on the point of dying from hunger and self-neglect, because they did not like to do anything apart; and when one of the halves died and the other survived, the survivor sought another mate, man or woman as we call them,—being the sections of entire men or women,—and clung to that.

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Each of us when separated, having one side only, like a flat fish, is but the indenture of a man, and he is always looking for his other half.

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And when one of them meets with his other half, the actual half of himself, whether he be a lover of youth or a lover of another sort, the pair are lost in an amazement of love and friendship and intimacy, and one will not be out of the other's sight, as I may say, even for a moment: these are the people who pass their whole lives together; yet they could not explain what they desire of one another.

Thales and Theophrastus were pro-celibacy, but does Plato think celibacy inhibits man's perfection?

What other philosophers believed that one is imperfect if one does not find and unite with one's "other half"?

Answer 1

I confine my remarks to Plato, who dominates your question

Plato, Aristophanes & the Symposium

Plato does not identify himself or the Platonic Socrates with Aristophanes' view. Aristophanes was a comedic playwright and he is here represented as in humorous mood, engaging in a jeux d'espirit. The story of the original three sexes and of Zeus' bipartition, with each half of a human being yearning and searching for its complement, is not offered or meant to be taken as a serious philosophical view - certainly not as Socrates' or Plato's - which is not to say that it lacks a certain profundity and suggestiveness.

Plato and marriage

Humankind's ultimate perfection, which is perhaps most fully elaborated in the Republic, is a state of eudaimonia or well-being, the true and absolute human good, in which a moralised psyche, "doing well" (eu prattei), practises justice or dikaiosune as the health of the soul. (Republic, IV.444c-445b et passim.)

At no point in the Republic or elsewhere does Plato suggest, so far as I know, that 'celibacy inhibits man's perfection'. On the contrary for the guardian class in the Republic, the phulakes, marriage is replaced by a communal arrangement in which after procreation, involving purely temporary and functional unions, no child knows its parent or parent its child (Republic, V. 460 ff.) Plato sometimes calls these unions 'marriages' [M1] but the term carries in this flattened-out usage no sense of lasting fidelity to and intimacy with another individual person [M2].

Unions of the M1 sort are necessary because procreation is essential to the continuation of the state. But nothing, and certainly not marriage in the sense of lasting fidelity to another individual, must weaken or undermine the guardians' properly single-minded concern with the activity of ruling. If acccompanied by marriage, sexual activity would be apt to deflect the guardians' from vital public to selfishly private and personal preoccupations. (Republic, V passim.)

Marriage as a concession to the elderly

Of course, when women and men pass the age for producing children, we shall declare them free, presumably, to have sex with anyone they like ... [GT: but injunctions against incest qualify this freedom.] ... (Republic, V.461b-c; Plato, The Republic, tr. T. Griffith, Cambridge: CUP, 2000: 159.)

At this stage there is no harm in marriage as lasting fidelity to and intimacy with another individual person [M2]. The elderly guardians, having passed out of public life and no longer responsible for the self-denying rigours of ruling, can harmlessly enjoy what pleasures remain to them.

Here I have concentrated on Plato's prescriptions for marriage - M1 & M2 - within the guardian class. He is more relaxed about marriage among the bulk of the population. But then, the general population are incapable of full human excellence on Plato's view, so what applies to them sets no standards for human excellence and the institutions, such as marriage, appropriate to it.