The non-Pauline Letters - what do we mean by that description? The negative suggests that we are dealing with somewhat marginalized texts compared with Paul. Many of our texts have indeed become cinderellas, though one comes from a theologian worthy to rank alongside Paul and 'John'; and the rest are increasingly seen as intriguing, for they enable access to the development of diverse traditions within early Christianity. Comparing and contrasting these makes study of these apparent 'oddments' rewarding. For this reason we shall keep them all in play alongside one another. But first to identify them.
Associated with the Pauline tradition, but definitely to be distinguished from Paul's work, is the Epistle to the Hebrews. Even if ascribed to Paul in the process of canonization, this work does not bear his name, and the Church of the third century CE knew not whence it came: one suggested Barnabas (Tertullian), one supposed Paul had written it in Hebrew and Luke translated it (Clement of Alexandria), one knew that Clement of Rome had been suggested but concluded that only God knows the author of the Epistle to the Hebrews (Origen).