Welcome back to Five-Point Haskell! This is my attempt to codify principles of writing robust, maintainable, correct, clear, and effective code in Haskell and to dispel common bad practices (or, heresies) I have run into in my time. In the last post, we talked about Total Depravity, which is about treating any mentally tracked constraint or condition as inevitably leading to a catastrophe and denouncing the reliance on our flawed mental context windows. However, stopping here gives us an incomplete picture. Firstly, types aren’t just about preventing bad behaviors. They’re about designing good code. Secondly, there is only so much you can do by picking careful structures and making invalid states unrepresentable. These are still human tools with human flaws. The next point, to me, is about an aspect of the type system that I see little coverage of, but is a doctrine of design that I reach for in almost everything I write. It’s about leveraging the unyielding properties of math itself to take care of our fate, even when we are unable to structure our types well. So, when writing Haskell, remember Unconditional Election. Unconditional Election: The power of the forall to elect or reprobate instantiations and implementations through parametric polymorphism. These properties aren’t based on any conditional ad-hoc aspect of types, but are truly unconditional, predestined by universal quantification.Surrender your control to parametric polymorphism in all things. Embrace the “free”-dom of “Free Theorems” from one of Haskell’s greatest unexpected strengths: the type parameter.