As Athanasius used it in these ways, physis had an overall slant deriving from the Christian understanding of God in his active relation to the world he has created and continues to sustain by his creative presence within it. It has a distinctively dynamic rather than a static sense, for the old Greek idea of an unchanging nature known only through static patterns and immutable relations (e.g. in classical mathematics or geometry) is set aside. Physis describes actual reality which confronts us in its own independent being, and which is known in accordances with its own inherent force or natural force in virtue of which it continues to be what it actually and properly is. This concrete use of physis as synonymous with what a thing actually and essentially is, with reality, understandably excludes any abstract notion of physis as signifying some general or universal ‘nature’, and so it operates outwith the orbit of the Aristotelian distinction between primary and secondary ousia. To know God kata physin, in accordance with his own nature, is to know him under th eimpact of his distinctively divine energeia, that is, to know him through a living empirical relation determined by theopoiesis. Thus Athanasius insisted that theologia and theosebeia, theology and godliness, belong inseparably together: for genuine knowledge of God arises only within an intellectual experience of his transcendent reality and majesty, and is maintained in the continuous context of worship, prayer, holiness and godly living. That is to say, God being God, the empirical and the theoretical, the religious and the theological, are ultimately and finally indivisible in our experience and knowledge of him.
T. F. Torrance, Divine Meaning (Edinburgh: T & T Clark, 1995), 211-212.