Real people and virtual bodies: How disembodied can embodiment be?

It is widely accepted that embodiment is crucial for any self-aware agent. What is less obvious is whether the body has to be real, or whether a virtual body will do. In that case the notion of embodiment would be so attenuated as to be almost indistinguishable from disembodiment. In this article I concentrate on the notion of embodiment in human agents. Could we be disembodied, having no real body, as brains-in-a-vat with only a virtual body? Thought experiments alone will not suffice to answer this Cartesian question. I will draw on both philosophical arguments and empirical data on phantom phenomena. My argument will proceed in three steps. Firstly I will show that phantom phenomena provide a prima facie argument that real embodiment is not necessary for a human being. Secondly I will give a philosophical argument that real movement must precede the intention to move and to act. Agents must at least have had real bodies once. Empirical data seems to bear this out. Finally, however, I will show that a small number of aplasic phantom phenomena undermines this last argument. Most people must have had a real body. But for some people a partly virtual, unreal, phantom body seems to suffice. Yet though there is thus no knockdown argument that we could not be brains-in-a-vat, we still have good reasons to suppose that embodiment must be real, and not virtual.