a theological term of the same import with co-essential, denoting something of the same substance with another. It is generally used to designate the relationship subsisting between the Father and the Son, as an equivalent to the term hypostasis, adopted by the councils of Antioch and Nice to express the orthodox doctrine more precisely, in opposition to the errors of Arius. (See Arius.) Sandius and others maintain that the word consubstantial was unknown till the time of the council of Nice. It was, however, proposed to the council of Antioch, and rejected there, according to Athanasius, only because it was supposed to imply the idea of a pre-existent matter.