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Clark & Chalmers (1998) provided the well-known case of Otto, where a person with Alzheimer's disease, Otto, always carries around a notebook with important information that he can't store in the head. They argued that Otto believes the information in the notebook. The notebook realises an "extended belief." Their main argument is a functionalist one. From the functionalist point of view, the notebook is equivalent to the neural realisers of biological beliefs.

In the extended mind literature, the main objection has been about the very idea that the notebook can realise a belief. Typically, critics deny the functional equivalence between the notebook and biological beliefs by citing some fine-grained functional differences between them. In this paper, I provide a new objection according to which the notebook does realise a belief but the belief does not belong to Otto. Otto does not believe the information in the book. It is rather the composite system consisting of Otto and the notebook who believes it. This response shares the basic idea with so-called the system reply to the Chinese Room argument. According to the system reply, the person in the Chinese Room does not understand Chinese when he simply follows an instruction book. It is rather the composite system consisting of the person and the instruction book who understands Chinese.

This response also saves functionalism from the challenge by Sprevak (2009). Clark & Chalmers endorse extended beliefs because functionalism implies it. Sprevak, on the contrary, rejects functionalism because it implies extended beliefs. More precisely, he argues that functionalism, if it implies that Otto believes information in his notebook, implies an absurd version of extended beliefs in which a person, when he randomly picks up a book from a library shelf, believes everything in the book. The implication is absurd even for Clark & Chalmers. Thus, functionalism needs to be rejected. I argue, in response, that the person in his library case does not believe everything in the book. It is rather the composite system consisting of the person and the book who believes everything in the book. And, it is far from obvious that this is an absurd implication.

(Kengo Miyazono)