in Theology, a term of like import with co-essential; denoting something of the same substance with another. The orthodox believe the Son of God to be consubstantial with the Father.

The term ἐνόμοσις, consubstantial, was first adopted by the fathers of the councils of Antioch and Nice, to express the orthodox doctrine the more precisely, and to serve as a barrier and precaution against the errors and subtleties of the Arians; who owned every thing excepting the consubstantiality.

The Arians allowed, that the Word was God, as having been made God; but they denied that he was the same God, and of the same substance with the Father: accordingly they exerted themselves to the utmost to abolish the use of the word. The emperor Constantine used all his authority with the bishops to have it expunged out of the symbols; but it still maintained itself, and is at this day, as it was then, the distinguishing criterion between an Athanasian and an Arian.

Sandius will have it, that the word consubstantial was unknown till the time of the council of Nice; but it is certain it had been before proposed to the council of Antioch, wherein Paulus Samotracenus had been condemned; though it had there the fortune to be rejected. Curcellaeus, on the other hand, maintains that it was an innovation in doctrine in the council of Nice, to admit an expression, the use whereof had been abolished by the council of Antioch.

According to St Athanasius, the word consubstantial was only condemned in the council of Antioch, inasmuch as it implied the idea of a pre-existent matter, prior to the things formed thereof; now, in this sense, it is certain, the Father and the Son are not consubstantial, there having been no pre-existent matter.