Christos Yannaras is one of the people we perhaps shouldn't ignore. In the Orthodox Church he's like Rowan Williams crossed with Stanley Hauerwas crossed with John Milbank. Maybe. Andrew Louth says that he is 'without doubt the most important living Greek Orthodox theologian'. Bet you feel about about not having heard about him now, huh?
Yannars' On the Absence and Unknowability of God takes a classic contemporary Orthodox-theological approach: he highlights a problem in Western thought, explaining why it's the Catholics' fault, and argues that if we'd just stayed Orthodox everything would have been fine. In this case, the problem is the death of God. Nietzsche announced that God was dead, and he's sometimes blamed for the subsequent growth of atheism in the West. But Heidegger argues that it's not Nietzsche's fault: all he was doing was prophetically announcing the imminent failure of European metaphysics. He says that European thought has basically turned God into nothing more than an anchor for everything else: God is there so we can explain why the universe made sense, so we can say that there's some original source from which everything else comes. God is the answer which puts a stop to the endless question: but why? Eventually, the answer is 'Because God'. Why do we exist? Because God created us. How can we trust our reason? Because God is rational and God came first. As soon as we start to use God like that, there's always the possibility that someone will come along and prove that there isn't any guarantee that we're rational, and so the whole idea of God will collapse, which is roughly what Yannaras thinks has happened in the West.
Apophatic theology, in this God-logic, ends up being part of the problem. If we can never fully understand the rational principle (God) on which everything else depends, we can start asking questions. We get skeptical, we get agnostic and then, bang! All of a sudden, we've become Richard Dawkins. But for Yannaras, God was never meant to be an axiom, a first principle, a logical necessity. We have a relationship with God, who loves us, and apophatic theology isn't meant to be about a logical incomprehensibility at the foundation of all being, it's meant to be about the fact that we can never fully articulate our experience of loving and being loved by God.
So for Yannaras, Heidegger and Nietzsche aren't atheists exactly, but point us towards a better, more plausible idea of God. Instead of thinking they understand what God is and how he caused everything, they leave God's place empty. God isn't dead, God is absent or unknowable. To think about how we come to know God, Yannaras uses the Eastern distinction between God's energies and God's essence. God's essence is, er, the essence of God, God in Godself. God's energies are God's activities in the world, creating, redeeming, and all that shebang. We can know God's energies but not God's essence, so knowing God through the world is a bit like knowing Banksy only through his artwork, or knowing Salinger only through Catcher in the Rye. An artists' work can tell us a lot about the artist, but they can't tell us what the artist is like in themselves.
So apophatic theology for Yannaras is important for two reasons: firstly, because of the unbridgeable divide between God's essence and God's energies, which means we can never speak about God's essence; and secondly because language always falls short of the richness of relationships: with God, we can experience more than we can speak of.