The real world is mutable in some sense, but our thinking, even in the most trivial exercises, works by detaching _objects_ them from their physical nature and building immutable _ideas_. Thinking is a struggle trying to find what is necessary in a contingent world, trying to find essence in a world of form. That is why values and immutability are so useful for modeling, architecture, and building resilient software.

I talked more about this in this MeetingC++'17 talk: https://www.youtube.com/watch?v=NMol_5-2owo