I have been thinking about the concept of Hypostatic Union (hypostasis). This concept was discussed among the Christian philosophers. It refers to the incarnation of Divinity. I will not discuss Christian theology. Instead, I will start by mentioning Leibniz’s interpretation of the Hypostatic Union. This gives me an opportunity to say few words on mind and matter.
C. Mercer and R.C. Sleigh, Jr. explain Leibniz’s argument as follows:
“The [hypostatic] union is made out of two elements, one active, one passive; the active element subsists per se, but can only act through the other; the passive element need not subsist per se, but is the means by which the active element acts. Moreover, according to Leibniz, although God does not need a passive element through which to act, created mind does. This means that in order for there to be any activity in the created world, hypostatical unions are required. Further, it is not enough that the active element acts some of the time, it must act constantly on the passive element. The idea seems to be that when the acting stops, so does the union. Thus, according to Leibniz, A and B are hypostatically unified if and only if the active element is constantly acting on the passive element and the latter is its ‘immediate instrument’ of acting.” 
According to Leibniz the active element is the mind and the passive element is the matter. Mind is the source of activity but the action can only occur through matter.
“[Leibniz] inserts created mind between God and body qua matter and withdraws the claim that God causes the motion in the corporeal substance. Instead, God creates mind so that it may act as ‘God’s instrument’.” 
This is very interesting and I see parallels with the Eastern Philosophy. Before I can make comparisons I need to give you some background. According to Tantra Yoga space-time-matter emanated from the Cosmic Mind. Unit minds (minds of organisms) emerge from space-time-matter at a later stage of the Cosmic Cycle. Unit minds emerge from matter because matter was mind in the first place. This is different from the idealistic philosophies. We are talking about emanations and transformations of the One. We are not dismissing matter merely as illusion. In fact, mind cannot function without matter. Mind and matter are interdependent.
Tantra Yoga perspective on mind/matter duality is also different from Leibniz’s understanding. There are some similarities, however. His insistence on mind being the activator and his reminder that mind acts on matter constantly could be considered as similarities.
There is a reason why matter was formed. Without matter the “Cosmic Inversion” would not have happened. At the end of the first phase (involution) of the Cosmic Cycle, the Cosmic Inversion happens when matter reaches its nadir of crudity. At the nadir the matter is at its most condensed state. The creative momentum still pushes towards more compression but matter cannot be compressed any more. At this point the unit consciousness immanent in each particle begins to unfold and starts its long journey towards liberation.
We started the story with the Cosmic Mind, but the story actually begins with Consciousness the infinite ocean of love and bliss which is the ultimate reality.
Absolute Unqualified Consciousness –> Qualified Consciousness –> Cosmic Life –> Cosmic Mind –> space-time-matter –> Organism –> Unit Mind –> Unfolding of the Unit Consciousness –> Expansion of the unit mind –> Merger of Unit Mind with the Cosmic Mind –> liberation of the Unit Consciousness –> Absolute Unqualified Consciousness
Unit Consciousness = Atman = Soul = Divine Spark = Reference to the Whole = Witnessing Entity = Life giving nucleus
Absolute Unqualified Consciousness = Nirguna Brahma
(People sometimes use the word Spirit to refer to Consciousness. The word spirituality is derived from the Spirit. Spirituality is about love which is the same as Consciousness. Spirituality is not to be confused with “spiritualism” which has nothing to do with love.
We should differentiate between the mind of an organism and the mind-dimension of its constituents. The mind of an organism is the collective-mind. Even elementary particles have a mind-dimension but this is different than the collective-mind of an organism. When protons and electrons come together to form an atom their mind-dimensions come together as well. When atoms come together to form a molecule their mind-dimensions merge. Similarly when molecules come together to form an organism the mind-dimensions of the molecules form a collective. That collective mind which is known as the “unit mind” controls the life energy of the organism. The matter dimension of the organism is controlled by the life energy and the life energy in turn is controlled by the unit mind.
I.S.(2) mentions the mind/matter duality as symbolized by the golden equation g-1/g=1. This duality applies to all units of manifestation. Each unit has a space-time-matter dimension and a mind-dimension which is the inverse/dual of the space-time-matter. In the case of elementary particles the mind-dimension is known to physicists as “intrinsic properties” such as charge and spin.
In the involution phase of the Cosmic Cycle there are no organisms and no unit minds but each particle and structure has that mind-dimension and the nucleus.
In the second phase of the Cosmic Cycle (evolution), organisms, animate structures and the unit minds emerge. Until this point there is mind/matter duality. After this point there is mind/body parallelism. Once the Cosmic Inversion is initiated the mind/body parallelism starts. This means that after this point the unit minds maintain their independent existence. When the organism dies the memory-kernel (unrealized reactions to actions) of the unit takes shelter in the soul. When the memory-kernel establishes parallelism with an organism with the help of the Cosmic Mind a new life starts and the unit mind starts reaping the results of its unrealized reactions. Rebirths continue until the memory-kernel dissolves in the Cosmic Mind. This can be a long journey because each new life brings more complications and entanglements. One secret that saves us from suffering is the practice forgiveness. By letting go of the hurt and the emotional attachments to the results of action the merger with the Cosmic Mind will eventually happen.
I have to say few words on the traditional interpretation of hypostasis. Divinity does not need to incarnate. Divinity is incarnated from the very beginning. Divinity is immanent in creation. This, however, does not mean that the Universal Teacher never incarnated in the traditional sense of the word. I firmly believe that the Universal Teacher uses us all to deliver messages all the time and comes closer during crisis times. This happened many times at many places. The historical personalities have different names but the Universal Teacher who teaches through them is the same.
 “The Cambridge Companion to Leibniz”, edited by Nicholas Jolley, ISBN 0-521-36769-7
* I thank James M. Emmerling for making me think on the meanings and of the terms “involution” and “evolution” as well as the “inversion” and “extraversion.”