" One must know that operation (energia) is one thing, what is operative (energetikon) another, that which is operated (energema) another, and yet another the operator (energon). Operation, then, is the efficient and essential (ousiodes) motion of the nature (physeos). And that which is operative is the nature (physis) from which the operation proceeds. The operated is the effect of the operation. And the operator is the person (hypostasis) who performs the operation. "

― John of Damascus , An Exact Exposition of the Orthodox Faith