2 Books on Shakespeare: "Dualities" and "Multiplicity"

When I decided to take another look at Shakespeare, I sent for books with relevant titles, but now that I see two of these books’ indices (1, 2), I find that their titles don't refer to Shakespeare’s psychological dividedness (dissociative identity or multiple personality), which I should have guessed. The laugh’s on me.

1. Marion Bodwell Smith. Dualities in Shakespeare. University of Toronto Press, 1966.

2. Brian Gibbons. Shakespeare and Multiplicity. Cambridge University Press, 1993.