Having nil (NULL, undefined whatever) that is falsey as is customary in Lisp/ Clojure is quite useful - the language family depends on it. Most things deal with

Having nil (NULL, undefined whatever) that is falsey as is customary in Lisp/ Clojure is quite useful - the language family depends on it. Most things deal with it very well and it is a useful distinction that something wasn't setup or didn't return any meaningful value for whatever reason. Clojure has a powerful meta-data system which could be used for checking for errors if Clojure didn't depend on the host platform for that. Also, it seems, Common Lisp also has some ideas about how to handle things more or less in-line with other code without having a special system that you can't see most of the time. Btw. some of this can go very deep in the technology stack, there were computers (https://en.wikipedia.org/wiki/Ternary_computer https://en.wikipedia.org/wiki/Ternary_computer) with ternary logic (https://en.wikipedia.org/wiki/Three-valued_logic https://en.wikipedia.org/wiki/Three-valued_logic). Such a computer could improve many aspects of computing, e.g. density and therefore efficiency. It could improve reliability (things could be more explicit). You could divide by 3 precisely and efficiently. It could improve our understanding of logic by making this for most of us alien concept to a more practical and widespread tool.