Saying a value is "unknown" means making no assumptions about the value. It might be a null, a number, a function, you don't care because you aren't going to do

Saying a value is "unknown" means making no assumptions about the value. It might be a null, a number, a function, you don't care because you aren't going to do anything with this value. If you call() it, or read.some.property, TS complains because you're making assumptions about the object that TS did not ensure.