This discussion is just going to reduce down to a runtime tag vs formal type definition. This particular article is using the term type to mean formal type, and

This discussion is just going to reduce down to a runtime tag vs formal type definition. This particular article is using the term type to mean formal type, and my comment is also under this assumption. Under that definition Ruby does have a null type system. That's not a moral judgement of it's design, it's just a fact that follows from the definitions. Rather than debate this for the gazillionth time, I'll just point you at tel's article which breaks it down very nicely: http://tel.github.io/2014/07/08/all_you_wanted_to_know_about_types_but_were_afraid_to_ask/ http://tel.github.io/2014/07/08/all_you_wanted_to_know_about...