Type checking is a symptom, not a solution

> The standard answer is scale. “Small programs don’t need types,” the reasoning goes, “but large programs become unmaintainable without them.”

This is not accepted wisdom at all.

He's even more wrong when the Python typing system allows us to catch bugs in small scripts.

If the argument is that even small programs benefit from types, then I'd agree. In the context of Typescript for example, leaving types out is hiding vital information needed for reading the code. Without it, you must infer that information on reading it, and you very well may infer wrong, incorrectly spotting a place where a function that appears to take a number is passed a string. To know if that's a bug, you must read the called function explicitly for the case to determine if an optional conversion is applied. And of course the inverse is even worse, because you may come to assume that all the functions taking numbers are also taking care to convert strings should they appear, when in fact no such assumption can be made.

I'm of the mind that the modern resurgence of typed programming languages is mainly the revelation that you can build your contracts directly into the structure of the code without necessarily needing additional (imperative, runtime!) assertions or physically separated unit tests to validate those assumptions as the software evolves. It's just inlining a certain kind of assertion or test directly into the declarations of the code.