Abū ‘Abd Allāh ibn al-Haysam:

“Chapter Four: Concerning His Oneness in Essence

“The Christians claim that God—exalted is He above what they say—is three hypostases, one Lord. Some explain the hypostases as persons, while others describe them as distinctive properties.”

He said: “Those who affirm God’s oneness say that God is one in His essence, possessing neither hypostases nor parts. The Christians argue: ‘You agree with us that God, exalted be His mention, has always possessed life and speech. That is what we mean by saying “three hypostases.”’”

He said: “The reply is to say to them: In our view, life and speech are two attributes of His essence; they do not have the status of the essence, nor does the name ‘God’ apply to them. Rather, God is the One described by them, not the attributes themselves. Nor can any acts of lordship rightly be attributed to them, for life and speech do not act. Rather, the One who lives and speaks acts: God, who possesses these two attributes.

“Your position is different, for you have made the Spirit and the Son two hypostases to which the name ‘God’ applies. In your view, acts of lordship are attributed to the Father, the Son, and the Holy Spirit collectively. You have thus treated them like the constituent parts of a human being, which collectively bear the name ‘human being’ and to which, taken together, his actions are attributed. This is