James Buchanan

“It has been said, indeed, that the faith of the primitive Church was extremely simple, — that it was ‘a life rather than a creed,’ — that few, if any, of the doctrines of Scripture had as yet been developed and defined, — and that Theology had not then assumed a systematic form. This statement is true, so far as it is meant merely to affirm, that the articles of faith were less rigorously reasoned out, and often more vaguely stated, before they were subjected to the ordeal of controversial discussion; for this holds good of every age; but it is not true, if it be understood to imply, either that the primitive Church did not believe, in substance, the self-same doctrines which were afterwards defined, or that her members were incapable of giving a sufficient reason for the hope that was in them. The primitive Church was instructed by the ministry of the Apostles, and continued to be nourished by the Gospels and Epistles; she was the aggregate of all those individual churches, — at Rome, at Ephesus, at Corinth, at Philippi, at Colossae, at Thessalonica, — to whom Paul addressed his profound arguments, in the confident persuasion that they would be understood by those to whom he wrote; and the controversies with false teachers, which were expounded in his writings, were surely sufficient to give them clear and definite views of the doctrines of Grace. The doctrine of Justification, in particular, was so thoroughly discussed in the writings of the Apostles, and that, too, in the way of controversy both with Jews and Gentiles, that their immediate successors had no occasion to treat it as an undecided question; — they found it an established and unquestioned article of the common faith, and they assumed and applied it in all their writings, without thinking it necessary to enter into any formal explanation or proof of it.”
― James Buchanan, The Doctrine of Justification