In this talk Erik Meijer surprised me by saying functional programming is not about immutability (at the end) which is talked about a lot by functional programm

In this talk Erik Meijer surprised me by saying functional programming is not about immutability (at the end) which is talked about a lot by functional programmers and then refers to his paper, which lays out his thoughts in greater detail: The Curse of the Excluded Middle: "Mostly functional" programming does not work by Erik Meijer https://queue.acm.org/detail.cfm?id=2611829 https://queue.acm.org/detail.cfm?id=2611829