Stanisław Lem's short story Are you there Mr. Jones?, first published in 1955, is set in a courtroom. The plaintiff is Cybernetics Company – a provider of prosthetics – and the defendant is Harry Jones, a race-car driver. It turns out that Mr. Jones, after a series of grave accidents, has had his entire body gradually replaced by prostheses. He is now deep in debt to the provider, Cybernetics Company, which consequently has sued him to reclaim their property. We aim to show that this short story illustrates important philosophical questions concerning personal identity and persistence over time, and that Lem in fact anticipates several of the main insights of functionalism, later introduced by Putnam (1967) and today a main contender for a theory of the mind. If the identity of Mr. Jones is constituted solely by his prostheses’ functional role, i.e., their causal relations to input, output and other bodily and mental states, Lem here gives us an early example of causal-theoretical functionalism.This brings us to the next question, implicitly raised by Lem: Is functional identity sufficient for personal identity? Is Mr. Jones the same person as he was before replacing all his body parts? In court, Mr. Jones argues for his continued personhood by appealing to memories from the past. This suggests the view that his persistence as a person depends on some form of psychological continuity, and we will discuss how the case of Mr. Jones relates to views on personal identity.