Further proof that the idea of SAME-SUBSTANCE was originally a Gnostic ( CONCEPT ) that slowly infiltrated Christianity:

JEROME (circa. 347 to 420 C.E.): “...Now compare the words of Origen, which I have translated word for word above, with these which by him have been turned into Latin, or rather overturned; and you will see clearly how great a discrepancy between them there is, not only of word but of meaning. I beg you not to consider my translation wearisome because it is longer; for the object I had in translating the whole passage was to exhibit the purpose which he had in suppressing the earlier part. There exists in Greek a dialogue between ORIGEN AND CANDIDUS THE DEFENDER OF THE HERESY OF VALENTINIAN, in which I confess it seems to me when I read it that I am looking on at a fight between two Andabatian gladiators. CANDIDUS MAINTAINS THAT THE SON IS OF THE SUBSTANCE OF THE FATHER, falling into the error of asserting a ProbolĂ© or Production. On the other side, ORIGEN, LIKE ARIUS AND EUNOMIUS, refuses to admit that He is produced or born, lest God the Father should thus be divided into parts; BUT HE SAYS THAT HE WAS A SUBLIME AND MOST EXCELLENT CREATION WHO CAME INTO BEING BY THE WILL OF THE FATHER LIKE OTHER CREATURES..." - (Hieronymus – Apologia Adversus Libros Rufini; Jerome’s Apology for Himself Against the Books of Rufinus; Addressed to Pammachius and Marcella from Bethlehem, a.d. 402. Book 2, Section 19, Page 512.)

The next quote is to show the use of the "...SAME-SUBSTANCE..." ( CONCEPT ) in Gnostic writings before it was used in Christianity:

CLEMENT OF ALEXANDRIA quoting THEODOTUS (EXTRACT 58): “Then after the Kingdom of Death, which had made a great and fair promise, but had none the less become a ministry of death, Jesus Christ the great Champion, when every principal­ity and divinity had refused, received unto himself by an act of power the Church, that is, the elect and the called, one (the spiritual) from the Mother, the other (the psychic) by the Dis­pensation; and he saved and bore aloft what he had received and through them what was CONSUBSTANTIAL. For "if the first fruits be holy, the lump will be also; if the root be holy, then will also the shoots."...” - (EXTRACTS FROM THE WORKS OF THEODOTUS AND THE SO-CALLED ORIENTAL TEACHING AT THE TIME OF VALENTINUS [Theodotus, a second-century Valentinian gnostic, that were compiled by Clement of Alexandria]. Translation by Robert Pierce Casey, The Excerpta ex Theodoto of Clement of Alexandria (Studies and Documents 1; London: Christophers, 1934), 40-91.)

There are many examples of the same-substance ( CONCEPT ) of the Gnostics within both sources quoted above.

See Irenaeus, particuarly in Keble's translation of the Greek version of Book 1 of Adv Haer. 

The Gnostic concept is blended with Christian concepts and mutated into the evolutionary proto-plasim from which the Tri{3}nity will slowly ooze out and take incremental steps toward influencing the minds of those already trained in and pre-disposed to Philosophy within Christianty.