The Apostle John tells us, quite clearly, in his first epistle, fourth chapter that the key to knowing that a messenger is from God is that he will agree/teach/declare that Jesus Christ is come in the flesh. We LDS sometimes use this as a proof-text for the validity of the angel Moroni, and indeed, the Book of Mormon itself, both of which testify that Christ came in the flesh. It counters nicely the wresting of Paul's words to the Galatians about a hypothetical angel with another gospel that are