'The Son' was indeed a creature and indeed 'of a different substance' because he was a mortal like us who became united with Jesus when he sat on the throne. This is the great secret of the Monarchian position (that dates back to Marcion) that never gets out.
The unity of the Godhead happened AFTER the Resurrection. The two became one. The flesh and glory were united but on the throne.
That is why Mark (and all his successors) are called Papa.
The little boy disciple in the gospel was 'the Son' who was adopted by the Father and ultimately sat together as one glorious being on the throne after the Resurrection.
All bishops and presbyters are named from the Papa who is the living representative of 'the Christ' (the Papa is said to this day to sit 'instead of' or in place of Christ).
The mystery is wholly contained in the ecclesia.
If you are interested in reading how this observation fits within my greater understanding of the workings of Secret Mark WITHIN the contemporary Alexandrian Church please go here
If you want to read more about how Alexandrian Christianity was rooted in the Jewish traditions of Alexandria, Philo of Alexandria and more feel free to purchase my new book here
