Original article can be found at : http://www.journalofphilosophy.org/ Copyright The Journal of Philosophy, Inc.On the basis of two argumentative examples plus their ‘parity principle’, Andy Clark and David Chalmers argue that mental states like beliefs can extend into the environment. I raise two problems for the argument. The first problem is that it is more difficult than Clark and Chalmers think to set up the Tetris example so that application of the parity principle might render it a case of extended mind. The second problem is that, even when appropriate versions of the argumentative examples can be constructed, the availability of a second, internalist parity principle precludes the possibility of inferring that the mind extends. Cho...