I think he's speaking specifically of the Algol-derived languages that the article is talking about, i.e. C, C++, Java, etc. Other languages (eg. SML, Ocaml, Haskell, and Rust) force you to make None an explicit value in an algebraic type (eg. Maybe/Optional), and that's what the article is arguing for. In dynamically-typed languages (Python, Javascript, Ruby) the question is irrelevant because there's no static type checking anyways. Static type systems bolted on top of dynamic languages (eg. CMUCL, Closure Compiler, TypeScript, Python typing) often get this right - they treat a nullable type as distinct from a non-nullable one and perform checking upon entry. There're also some languages (Kotlin, Java8 with @NonNull) that are fundamentally saddled with null because it's part of the platform APIs, but have built layers on top of it similar to these to perform nullability checks.