I n this chapter we shall begin our examination of the evidence common to two or more of the theories, and the first we shall deal with is the argument from parallelisms. A literary parallelism, as its name implies, is a passage occurring i n a work by one author which bears a marked resemblance i n thought and expression to a passage occurring i n a work by another author. W h e n such a parallelism is discovered it naturally suggests some connection between the two works. This connection may result from any of the following causes:

(1) Deliberate plagiarism. (2) Unconscious plagiarism. (3) Derivation from a common source. (4) T h e use of a commonplace expression. (5) Coincidence.