[Haskell-beginners] type question

Hello, I'm now following the book Programming in Haskel by Hutton. IM now reading the chapter about types. But I don't understand this : False :: Bool True :: Bool ¬ :: Bool ---> Bool So False and True has the type Bool. That's clear. I find out that ¬ makes the opposite of True and False. But why is it also the type Bool --> Bool Roelof