Sadly you are confusing person and nature. The Father and the Son are one in nature, but the Holy Spirit is also one in nature with them;
I'm not confusing person and nature. The Father and Son are not only one in nature but one in being,and God as Being is a matter of person. The persons of the Trinity are one Being that we call "He".
and so, if I accepted your position, it follows that the Spirit would be the cause (aitia) of His own hypostasis, which is utter nonsense.
No,that doesn't follow from my position. The Spirit is caused by the Father and Son,so he is not the cause of his own person.
To put it another way, the theological position that you are advocating ultimately leads either to Sabellian Modalism, because it involves confounding the hypostatic uniqueness of the Father and the Son by making them into one and the same person / principle (arche),
No,it doesn't confound the uniqueness of the Father and Son,because they are still who they are. One is defined by Fatherhood and the other is defined by Sonship. The persons of the Trinity are collectively one principle,which is why Christian philosophers can call God the first principle.
or it leads to subordinationism and ditheism, because it makes the Holy Spirit essentially less than the Father and the Son since He alone (i.e., the Holy Spirit) cannot spirate a divine person, which involves at the same time a denial of His being co-essential with the Father and the Son. Now, these theological difficulties are quite simply a form of the Pneumatomachian heresy.
How does being breathed by the Father and Son as their own Spirit make the Spirit essentially less than they are? On the contrary,it makes the Spirit essentially what they are. But if you believe that the Father alone is cause of the Spirit,then you may as well deny that the Spirit is of the Son,and that the Son eternally has the Spirit of Sonship.
Is St. Basil a heretical subordinationalist when he says that the Spirit is third in dignity?
You are confusing the fact that there is a real distinction between hypostatic origination and energetic manifestation with the idea that there are separations within the Godhead. But a real distinction (i.e., a pragmatika diakrisis) does not involve a separation (i.e., a pragmatike diaresis), and that you are unaware of this fact is disturbing to say the least.
If the Son were not connected as person with the eternal origination of the Spirit,then they would be separated in eternity from each other,and there would be three gods with one nature.
Energetic manifestation is not a fact.
Energy is "personal" (i.e., it is enhypostatic), but it is not a person (hypostasis).
What is personal about God can't be distinguished from the persons of God without making a separation in God. Where the power and attributes of God are,God is there is person.
The primary error of Latin theology is its failure to distinguish between the Spirit as person and the Spirit as gift (energy).
The error of Greek theology is assuming there is such a distinction. The Spirit is always a person. If he were not,then he would not be a He,or God. There is no reason to think that the Spirit is shorn of personhood when he is sent as a gift to men. A person who is an eternal spirit can go anywhere.
That said, no man can receive the hypostasis of the Spirit because that would involve a hypostatic union between each individual Christian and the Holy Spirit, but there is only one hypostatic union and that occurred in the incarnation of the eternal Logos.
Christ was conceived with the hypostatic union. It was who he was intrinsically. Christians are united with God from without. We are not like that intrinsically. Christ told his apostles that the Spirit (he) would be in them,and he himself would remain in them.
John 14:17 The spirit of truth, whom the world cannot receive, because it seeth him not, nor knoweth him: but you shall know him; because he shall abide with you, and shall be in you.
John 14:22 Judas saith to him, not the Iscariot: Lord, how is it, that thou wilt manifest thyself to us, and not to the world?
John 14:23 Jesus answered, and said to him: If any one love me, he will keep my word, and my Father will love him, and we will come to him, and will make our abode with him.
Where in my post did I say that proienai is limited to temporal manifestation?
I said that the Spirit's movement from the Father through the Son concerns ". . . [His] eternal progression (proienai) or manifestation (phanerosis) as energy (energeia)."
That would mean that there is division within the Trinity,since the Spirit's energies are separated from his person in the procession,and persons are not being communicated with each other.