Antinomies and paradoxes were certified in all the sacred books, particularly in Heraclitus, Plotinus, Donne, Swedenborg, Nietzsche. From this comes his theory of the opposing psychological types,  objective and subjective; two terms which can give rise to a great deal of confusion, since his usage is a special one. From it comes his cyclic theory, as in the gyres. The interlocking, counter-rotating cones of the gyres, though they point towards the qualities of the sphere and circle, move in contrary senses. They are the result of the descent of man into the corporeal world. So we have the antinomies of hot and cold, moist and dry (the alchemical theory of the humours with which he was familiar from many writings); male and female; water and fire; the Yin and Yang (yen and yin).  Thus man runs his course between spiritual and corporeal, between the fire of spirituality and the lush green leaf; the tree that is half-flame and half-green foliage is a compressed symbol of this.
Every action, even the smallest, moves towards its opposite, and then relapses into its first condition. Thus a physical act progresses from inertia to violence, and returns to inertia again.  A civilization passes from barbaric materialism to a search for its opposite, the spiritual, aesthetic and intellectual achievement which is symbolized in part by Byzantium. Athens, Greece, Alexandria, types of the rational, is destroyed by the impact of the irrational in The Resurrection; the heart of a phantom is beating. Every personality desires its opposite. The cat and the moon, the earthbound and the heavenly body, are attracted and linked by material sympathy. Man not only seeks his opposite but always tries to become his opposite - to become what he would abhor if he did not desire it. He desires it because he feels that he needs, not merely the fullness and roundness of personality, but the dramatic complement of those whose lack has given rise to frustration. So the Saint would become the swordsman, the scholar-recluse the soldier and lover. In the mutations of history the same principle is perceived. If the Greek civilization is fully subjective, the Hebrew which precedes it must be objective. And this principle holds good for all ages, even the present.:
When a civilization ends, task having led to task, until everybody was bored, the whole thing turns bottom upwards, Nietsches transvaluation of all values.  
So it is in the supernatural world. Yeats accepted, wholly or partially, Plutarchs account of the Daemon, the guardian spirit; which is familiar from the dramatic presentation of that belief in Antony and Cleopatra . Plutarchs precepts have it that a strange living man may win for Daemon an illustrious dead man; but now I add another thought: the Daemon comes not as like to like but seeing its own opposite. 
In this way the fighting hero Cuchulain has for his daemons convicted cowards. Yeats daemon in Byzantium is death to his life, life to his death. It is another variant of the often repeated gnomic quotation from Heraclitus: Men and gods die each others life, live each others death. These are the words with which The Greek concludes The Resurrection .
On the initial premise of the antinomies most of Yeats metaphysic is based. We can see the invocation of the complementary aspects, or their imagined subvention, as a step in the progression towards unity. So
The image may take a multiplicity of forms. Imagined violence, leadership in war; horsemanship, in family tradition or in Robert Gregory; the fisherman; the roaring tinker or journeyman; Dante; Hector and Achilles; Swift and Berkeley in their assertion of the supreme intellect, sanctity without orthodoxy, that rejects Von Hügel, but speaks in favour of ancient heresies through Ribh the Hermit.
I do not think that any solution emerges in earthly being from this dialectic. The solution is in eternity, where we, and all lovers, are adrift on that miraculous sea. The poems and plans that sharpen the opposing polarities grow more brutal and more violent as the physical solution recedes. Crown of gold and dung of swine confront each other in A Full Moon in March, and
The thought might be Swifts, or Villons, or Odos. . Resolution of the conflict on a womans breast (as in The Wild Old Wicked Man) is momentary, a gesture or emblem of ultimate union. Even in Ribh at the Tomb . the angelic marriage may be illusory;
Only in the tiny fragment There is the assertion of this final unity in the classical symbol of the sphere:
There all the barrel-hoops are knit, There all the serpent-tails are bit, There all the gyres converge in one, There all the planets drop in the Sun. 
At the centre of Yeats view of the sexual act is the traditional one of both Hindu and Kabbalistic mythology. In it is symbolized the reconciliation of all opposites in the divine world. The lovers, the paired extremities, can achieve perfect unison only in the after-life; but earthly union may offer a Platonic shadow of the joy that is eternity. Perfect consummation would result in the cessation of time:
Oil, wick, candle, flame, torch are all traditional symbols, and for the antinomy we may remember Hamlet.
The same holds good in the relationships between men and women. Young, we discover an opposite through our love. When a man loves a girl it should be because her face and character offer what he lacks, the more profound his nature the more should he realize the lack and the greater be the difference. It is as though he  wanted to take his own death into his arms ..  Vacillation is implicit in the act of love. The Three Bushes concerns the Ladys attempt at a compromise. She will think herself spirit; the Chambermaid will provide the flesh:
So the woman in A Last Confession is aware, without illusion as to its spirituality, of the nature of the body:
But her vision includes the final perfection of spiritual union in death:
The wise man is aware of these antinomies, in himself and in the great men of history. He finds a precedent for living cautiously in obedience to the double thrust of mortality. Dante finds room among his virtues for lechery. There is ample justification from philosophy and psychology. 
Opposites can only be resolved in the after-life; and this contrived opposition is a necessary condition of life. Could these two impulses ... be reconciled all life would cease. True love is only possible in the divine world: 
- so that the intercourse of angels is as important to Ribh as it was to Milton and Swedenborg. The symbol of the divine world is, as always, the sphere which stands for divine perfection, symmetry, the mystery of completion:
This poem, Chosen, is one of the finest, and most complex, of the sequence A Woman Young and Old. The souls of the lovers are on the miraculous stream of the Milky Way, the V ia Lactea of the seventeenth-century imagination. It opens with Platos Myth of Er: the souls in heaven, resting between incarnations, choose the lots that represent their destinies in the after life. In it is embodied Plotinus essay, The Heavenly Circuit: the Zodiac-sphere is explained in A Vision . Yet none of the complexities could tarnish the magnificence of Yeats rhetoric.
The same antinomies pervade the material of the Celtic Revival. Were the dusty deeds ever capable of significant alignment with the Irish political situation, in 1798 or in 1916? How forced were the allegorical structures of, say, Cathleen-ni-Houlihan and The Countess Cathleen ? Was it merely good fortune that Oliver Sheppards statue should provide a credible link between Cuchulain and the Easter Rising? The ancient legends on which so much Yeatsian theory depended had even fewer roots in the Irish peasant memory than had the Mabinogion in the Welsh. After the first excitement of exploration the tensions were considerable. John Eglinton thought  that these ancient legends obstinately refuse to be taken up out of their environment and be translated into the world of modern sympathies: Jung and his archetypes were still unknown. The legends were, indeed, hardly familiar enough even for satire, though an attempt had been made by Eimar ODuffy in King Goshawk and the Birds ; the great field of traditional Irish satirical writing was .hardly opened by the ploughs of the Abbey . I suspect that George Moores wish was an empty one:
And, always, there was the real or potential conflict of the Celtic Revival with the Church; mainly because of the Protestant background of those that wrote of it. A.E.s worship of the Elder Gods was regarded with a slightly suspicious tolerance; his eccentricities no more than an embroidery on his very real services to the Department of Agriculture. Heresy had been found in The Countess, and it is difficult to appreciate the suspicion which Yeats had aroused. MacKenna wrote to A.E. of the hostile review of the Collected Edition, 1908-9 which the Editor of The Freemans Journal wanted to arrange:
 Song and its Fountains, pp.30-31.
 Wheels and Butterflies, 1934, p.103.
 This is the opening argument of the Summa of Aquinas.
 On the Boiler, p. 25. For a discussion of the debt to Nietszche, see Engelbergs The Vast Design.
 Per Amica Silentia Lunae, p.29.
 Collected Poems, p.180.
 Of Cluny.
 Coll. Poems, p.329.
 Solomon and the Witch, ibid., p.199.
 On the Boiler, p.22.
 Coll. Poems, p.313.
 See, passim. Martins Experiment in Depth; and Jungs The Secret of the Golden Flower, which Yeats had read.
 Coll. Poems, 102.
 Ibid., p.311.
 (B) pp.210, 240. See also Veronicas Napkin, Coll. Poems, p.270.
 See, in particular, Vivian Merciers The Irish Comic Tradition.
 Preface to The Bending of the Bough .
 Memoirs and Journals, p.38.