How many letters did Paul write?

A:

Thirteen epistles have been attributed to Paul. Only seven Pauline epistles are widely considered by biblical scholars to be genuine, and of these five have been shown by computer analysis to contain exactly the same writing or dictation style: Romans, 1 and 2 Corinthians, Philemon and Galatians. The two that may, with some confidence, have been written by Paul, but do not match the style of Galatians are Philippians and 1 Thessalonians.

However, references within 1 and 2 Corinthians suggest the existence of probably 2 additional epistles to the Corinthians, written during the same period.

Other epistles attributed to Paul were really written by anonymous authors long after the time of Paul.