All existent things can be grouped into ten categories, namely, essence, quantity, quality, relation, place, time, activity, passivity, possession and dependence; and these ten categories apply likewise to everything subsequently seen to pertain to essence. But God is supraessential essence, in which can be seen only relation and activity or creation, and these two things do not produce in His essence any composition or change. For God creates all things without being affected in His essence. He is Creator in relation to creation, and also its Principle and Master in that it has its origin in Him and is dependent on Him. But He is also our Father, since by grace He confers on us rebirth. Yet He is Father, too, in relation to the Son who is completely without any temporal beginning. The Son is Son in relation to the Father, while the Spirit is the projection of the Father, coeternal with the Father and the Son, being of one and the same essense.
Those who assert that God is only essence, with nothing to be seen in Him, fabricate a God who has neither creativity and energy nor relation. But if He whom they suppose to be God does not possess these properties, then He is neither active nor Creator, nor does He possess an energy; and neither is He Principle, Creator and Master, nor is He our Father by grace. For how could He be these things if relation and creativity are not to be envisaged in His essence? Furthermore, if relation is not to be envisaged in God’s essence, the tri-hypostatic character of the Godhead is also abolished. But He who is not tri-hypostatic is not the Master of all or God. Thus those who hold the views of Barlaam and Akindynos are atheists.
~St Gregory Palamas (Philokalia vol.4, pp.409-410)