Partial functions are the antithesis of this concept. They allow you to say "yeah dude, I can totally give you the first value in an empty list." Partial functions are like politicians: you can tell they're lying because their lips are moving. ("But Michael," you say. "Functions don't have lips!" Whatever, I'm waxing poetical.)

Alright, so plenty of languages screw this up. Haskell tells those languages "hold my beer."

Michael Snoyman: Haskell: The Bad Parts, part 2