They're both primarily based on lambda calculus. Although haskell on typed lambda calculus. They both emphasize purity over mutations. They both are designed to

They're both primarily based on lambda calculus. Although haskell on typed lambda calculus. They both emphasize purity over mutations. They both are designed to make higher-orderisms idiomatic. But the point isn't so much the features they share. I'd be the first to admit that Lisp and Haskell are very different. But functional programming in both is very much based on the same ideas. Claiming that they're as different as OO vs imperative is like saying that washing dishes by hand is as different to using a dishwasher as football is to baseball.