By essence I am not referring to doctrines or denominations or theology, but more to the "is-ness" of Christianity . What is its indispensable quality -- the quality that should be "essential" to all Christian doctrines, denominations, and theology but can also exist beyond any Christian doctrine, denomination, or theology?
Well, I think the "what it is" of Christianity is about relationships between beings, especially between the divine and the human, which serves common purpose; a relationship in which the divine and human "depend" on each other.
Classical, traditional, orthodox theology also refers to relationships between the divine and the human, but the "what it is" of classical, traditional, orthodox theology emphasizes a one-sided contingent relationship - man depends on God and needs God for everything, while God does not depend on or need man for anything.
Because God is an entirely different category of being (he is a being and the source of all beings) that does not need or depend on anything or anyone in order to be or to become (but God has no need to become anything because he already is everything and anything that can be).
This immediately raises questions about why this Omnigod – who has no need of anything and who is perfectly fulfilled as an independent being – would bother with Creation in the first place.
Classical theology always pounds the table about logic, but then goes on to explain Creation as a gratuitous act of love, which is fascinating when you consider that gratuitous means both "free" and "superfluous." Thus, God created of his own free will, but Creation itself is not necessary to God and God would be perfectly content without it.
Having outlined all of that, classical theology then goes on to insist that man still matters (why would he?) and that God is still "relational" (why would He bother)?
So, why does man matter? Well, because God decided man matters, that's why (no real "logical" explanation provided other than the notion that man should submissively worship God and thank God for everything and serve him even though God doesn’t depend on this worship, gratitude, or service).
Why does God want to establish relationships with us when he doesn't really need to? Well, because he loves us, even though he doesn't really need to love us because we are in an entirely different category of being and can never understand him. On top of that, it doesn't really matter if we love him or not because he doesn't depend on that love.
In fact, the only downside to not loving God is you end up spiritually destroying yourself -- but this spiritual destruction does not affect God in any way because he is perfectly and absolutely self-sufficient and not dependent on anything.
In my mind, this is not the essence – the what it is – of Christianity -- or at the very least, it shouldn't be.
The essence of Christianity - "the what it is" (I dislike these philosophical terms, but don't know how else to put it) should be relational - relationships between beings.
Most importantly, the relationship between the human and the divine – a relationship in which man needs God, but God also needs man.
The basis of this relationship is love. Not love as a virtue or love as an emotion, but love as a metaphysical reality.
The kind of love that is only possible between beings who see themselves in each other, who need each other, recognize a shared purpose, and freely commit to actively working toward a common goal – a common goal that elevates both man and God through the expansion of freedom and love.
Note: This post was inspired by a comment I left on Bruce Charlton's Notions.
Note added: What I have presented above is obviously a gross simplification of classical, traditional, orthodox theology, but the simplification serves a purpose. This purpose is not to label classical theology as all wrong, but rather to point out where classical theology can be deepened and expanded. Classic theology's glorification of God frequently comes at the price of debasing man. I believe any debasement of man is also a debasement of God. If it weren't, the demonic forces would not work so hard to debase man at every turn.