God is one because there is one Divinity: unoriginate, simple, beyond being, without parts, indivisible. The Divinity is both unity and trinity — wholly one and wholly three. It is wholly one in respect of the essence, wholly three in respect of the hypostases of persons.
For the Divinity is Father, Son and Holy Spirit, and is in Father, Son and Holy Spirit. The whole Divinity is in the whole Father and the whole Father is in the whole Divinity….
The whole Son is in the whole Divinity and the whole Divinity is in the whole Son; the whole Son is both the whole Divinity and in the whole Divinity….
The Divinity is not partially in the Holy Spirit, nor is the Holy Spirit part of God. For the Divinity is not divisible; nor is the Father, or the Son, or the Holy Spirit incomplete God.
On the contrary, the whole and complete Divinity is completely in the complete Father; the whole and complete Divinity is completely in the complete Son; and the whole and complete Divinity is completely in the complete Holy Spirit….
Therefore the Father, the Son and the Holy Spirit are one God. The essence, power and energy of the Father, the Son and the Holy Spirit are one, for none of the hypostases or persons either exists or is intelligible without the others.
~St Maximos the Confessor
If you make a habit of listening to spiritual teaching, your intellect will escape from impure thoughts.
God alone is good and wise by nature; but if you exert yourself your intellect also becomes good and wise through participation.