> an instance of 'prefer referential transparency', an idea from FP that you should always know what a variable is referencing.
The idea of "referential transparency" is that you should always be able to substitute a reference for its definition, or vice-versa, without changing the behavior of the program. This implies both immutability (so that duplicating a value doesn't change the result) and purity (so producing the value has no side effects and gives the same result no matter how many times you do it). It has nothing to do with knowing what a variable is referencing. If anything, functional programming encourages the use of generic functions which don't know or care what their variables are referencing (parametric polymorphism).