Perfect being theism, roughly the view that God exists and is perfect, is associated with Anselm of Canterbury (c. 1033-1109), and philosophical theology, partly rooted in Greek philosophy, more generally. Its origins seem to lie more in Athens than in Jerusalem, more in Greek thinking than in Jewish thought. Indeed, some are not so sure the biblical God is a perfect being. The idea that Jesus was a perfect being theist seems silly. Remarkably, however, in the Sermon on the Mount Jesus says the following:

“You therefore must be perfect, as your heavenly Father is perfect.”

Matthew 5:48 (ESV)

On a straightforward reading of the passage, at least in this translation, Jesus believes that the God of Israel is perfect. This reading cannot simply be dismissed, because it seems to have some support in the church fathers:

“But as God is eternal and rational, so, I think, He is perfect in all things. ‘Be ye perfect, even as your Father which is in heaven is perfect.'”

Tertullian, The Five Books Against Marcion

“…we must believe that God is in all things perfect, according to our Saviour’s word, which saith, Your Father in heaven is perfect: perfect in sight, perfect in power, perfect in greatness, perfect in foreknowledge, perfect in goodness, perfect in justice, perfect in loving-kindness: not circumscribed in any space, but the Creator of all space, existing in all…”

Cyril of Jerusalem, The Catechetical Lectures of S. Cyril

Moreover, that Jesus was a perfect being theist seems less incredible if we consider some passages from the Jewish thinker Philo (c. 20 BC – c. 50 AD):

“Do you doubt whether the imperishable, and everlasting, and blessed God, the Being endowed with all the virtues, and with all perfection, and with all happiness is unchangeable in his counsels, and whether he abides by the designs which he originally formed, without changing any of them.”

Philo, On the Unchangeableness of God

“He is free from all pain, and free from all fear; he has no participation in any evils, he yields to no one, he suffers no sorrow, he knows no fatigue, he is full of unalloyed happiness; his nature is entirely perfect, or rather God is himself the perfection, and completion, and boundary of happiness, partaking of nothing else by which he can be rendered better, but giving to every individual thing a portion of what is suited to it, from the fountain of good, namely, from himself; for the beautiful things in the world would never have been such as they are, if they had not been made after an archetypal pattern, which was really beautiful, the uncreate, and blessed, and imperishable model of all things.”

Philo, The Cherubim

Also, Jesus seems more generally to have held a very high view of God:

“No one is good except God alone.”

Mark 10:18 (ESV)

“…with God all things are possible.”

Matthew 19:26 (ESV)

“…the Father has life in himself…”

John 5:26 (ESV)

“And this is eternal life, that they know you the only true God…”

John 17:3 (ESV)