There's beautiful clarity in the articulation, and the essence is easy to grasp yet powerful. It reminds me a bit of Scott Wlaschin's Railway Oriented Programming (ROP) [0]. As a technique, ROP nicely complements "parse don't validate". As an explanation, it's similarly simple yet wonderfully effective.
I've a real admiration for people who can explain and present things so clearly. With ROP, for example, the reader learns the basics of monads without even realising it.