This book explores a neglected philosophical question: How do groups of interacting minds relate to singular minds? Could several of us, by organizing ourselves the right way, constitute a single conscious mind that contains our minds as parts? And could each of us have been, all along, a group of mental parts in close cooperation? Scientific progress seems to be slowly revealing that all the different physical objects around us are, at root, just a matter of the right parts put together in the right ways: How far could the same be true of minds? This book argues that we are too used to seeing the mind as an indivisible unity and that understanding our place in nature requires being willing to see minds as composite systems, simultaneously one conscious whole and many conscious parts.
In thinking through the implications of such a shift of perspective, the book relates the question of mental combination to a range of different theories of the mind (in particular panpsychism, functionalism, and Neo-Lockeanism about personal identity) and identifies, clarifies, and addresses a wide array of philosophical objections (concerning personal identity, the unity of consciousness, the privacy of experience, and other issues) that have been raised against the idea of composite minds. The result is an account of the metaphysics of composition and consciousness that can illuminate many different debates in philosophy of mind, concerning split brains, collective intentionality, and the combination problem, among others.