Blockhead is a theoretical computer system invented as part of a thought experiment by philosopher Ned Block, which appeared in a paper titled "Psychologism and Behaviorism".
Block asks us to imagine a conversation lasting any given amount of time.
He states that given the nature of language, there are a finite number of syntactically and grammatically correct sentences that can be used to start a conversation.
Block then asks the reader to imagine a computer which had been programmed with all the sentences in theory, if not in practice.
Block argues that such a machine could continue a conversation with a person on any topic because the computer would be programmed with every sentence that it was possible to use so the computer would be able to pass the Turing test despite the fact that — according to Block — it was not intelligent.