Adoption Into The Canon
ADOPTION INTO THE CANON
The first epistle may be reflected in some passages in 1 Clement and Ignatius, but this is not certain. What is clear is that it is included both in Marcion’s canon 32 and in the Muratorian Fragment, and it is quoted by name in Ireneus. No doubts seem to have been raised by it. Second Thessalonians is attested by Polycarp, and possibly Ignatius and Justin. It is included in Marcion’s canon and in the Muratorian Fragment. Ireneus quotes it by name.
Thus both letters were accepted in very early days; there seem to have been no doubts in the early church about their place in the canon.