A language L ⊆ A∗ is literally idempotent in case that uav ∈ L if and only if uav ∈ L for each u, v ∈ A∗, a ∈ A. Such classes result naturally by taking all literally idempotent languages in a classical (positive) variety or by considering a certain closure operator. We initiate their systematic study. Various classes of such languages can be characterized using syntactic methods. A starting ex...

Hamlet: Has this fellow no feelings of his business, that he sings at grave-making? Horatio: Custom hath made it in him a property of easiness. (Hamlet Act V, scene i) Hamlet is appalled by the gravedigger's insensitivity towards death and corpses. Horatio explains that the gravedigger is so accustomed to such things that he no longer shares Hamlet's seriousness. We contend that human dissectio...