Welcome to Light On Light Through, Episode 368, which I devote to consideration of tetrads for history and alternate history.   Don't know what tetrads are?  They're explained in the first few minutes of the podcast.

Read about Tetrads for History and Alternate History here.

Further reading on Tetrads: Laws of the Media (by Marshall McLuhan, with Preface by Paul Levinson); Tetrad Wheels of Cultural Evolution (Paul Levinson); Tetrad on the Selfie (Paul Levinson); Tetrads and Chiasmus: A Reclamation of the Tetrad Wheel (Matthew S. Lindia & Paul Levinson),

Further reading, listening to, viewing Alternate History: A Fiction Writer's Guide to Alternate History by Jack Dann; Paul Levinson's review of A Fiction Writer's Guide to the Alternate History; Paul Levinson's interview with Jack Dann; Paul Levinson's interview with Rufus Sewell, who starred in The Man in the High Castle series on Amazon Prime Video; Chuck Todd's interview with Paul Levinson about alternate histories; It's Real Life (alternate history about The Beatles by Paul Levinson, made into a radio play) 

Also -- a voicemail from Marshall McLuhan for me, in 1978