The 3 levels of functional thinking

I’ve noticed that people go through a certain journey when learning functional programming. I’ve classified it into three levels: 1) Distinction between Actions, Calculations, and Data; and learning to use them effectively 2) Higher-order thinking; and building abstractions from higher-order functions 3) Algebraic thiking; building coherent models with a focus on composition. This is a work in progress and I’d love your input.