17 As Jesus started on his way, a man ran up to him and fell on his knees before him. “Good teacher,” he asked, “what must I do to inherit eternal life?”
18 “Why do you call me good?” Jesus answered. “No one is good—except God alone. ”
So Origen reveals the implicit gnostic DUALISM
in the answer of Jesus, despite - or rather, just in virtue
- of the his explicit proclamation that "God alone
" is good.
There still remains to them, however, that saying of the Lord in the Gospel, which they think is given them in a special manner as a shield, viz., There is none good but one, God the Father. This word they declare is peculiar to the Father of Christ, who, however, is different from the God who is Creator of all things, to which Creator he gave no appellation of goodness. Let us see now if, in the Old Testament, the God of the prophets and the Creator and Legislator of the word is not called good. What are the expressions which occur in the Psalms? How good is God to Israel, to the upright in heart! and, Let Israel now say that He is good, that His mercy endures for ever; the language in the Lamentations of Jeremiah, The Lord is good to them that wait for Him, to the soul that seeks Him. As therefore God is frequently called good in the Old Testament, so also the Father of our Lord Jesus Christ is styled just in the Gospels.
(Origen, De princ
In a dualistic system, only the supreme Good god can be qualified as the unique only god. The other god is Satan.
Hence, Mark comes after