The periphery of the canon is not yet determined.
Marcion's 'New Testament', the first to be compiled, forced the mainstream Church to decide on a core canon: the four Gospels and Letters of Paul.
Marcion eliminated the Old Testament as scriptures and, since he was anti-Semitic, kept from the New Testament only 10 letters of Paul and 2/3 of Luke's gospel (he deleted references to Jesus' Jewishness).
Yahweh, the cruel God of the Old Testament, and Abba, the kind father of the New Testament. Marcion, a businessman in Rome, taught that there were two Gods: