The process of canonization of the New Testament was complex and lengthy. In the initial centuries of early Christianity, there were many books widely considered by the church to be inspired, but there was no single formally recognized New Testament canon. The process was characterized by a compilation of books that apostolic tradition considered authoritative in worship and teaching, relevant to the historical situations in which they lived, and consonant with the Old Testament. Writings attributed to the apostles circulated among the earliest Christian communities and the Pauline epistles were circulating, perhaps in collected forms, by the end of the 1st century AD.