An analysis of the philosophical and theological works of Philo of Alexandria and Pseudo-Dionysius the Areopagite reveals a very important metaphysical distinction between essence or nature (ousia) and energies or workings (energeiai) in God's being. The common goal of these thinkers is to express the truth about God's being and His existence. There are not two Gods, Transcendent and Immanent. If the transcendence of God supposes His unknowability, His immanent nature points some form of His knowability. So, to preserve monotheism, Philo of Alexandria and Pseudo-Dionysius the Areopagite introduce a metaphysical distinction between the essence or nature (ousia) and the energies or workings (energeiai) of God. In this philosophy and theology, God is unknowable in His essence and knowable in His energies. This metaphysical distinction is the basis of byzantine philosophy and theology.