Philosophers of mind and cognitive scientists have recently entertained the extended mind hypothesis, the idea that the mind and cognition extend beyond the boundary of the body. This talk will provide an overview of this hypothesis and some of the considerations that have arisen in debating its truth with an emphasis on addressing the question of why this debate matters to psychologists and cognitive scientists themselves. The short answer to this question is that the debate both reflects deep-seated views of what cognition is and what constitutes an appropriate way to study it, and points the way to new opportunities for transdisciplinary work on the nature of cognition.