It may soon be possible for neurotechnology to connect two subjects' brains such that they share a single token mental state, such as a feeling of pleasure or displeasure. How will our moral frameworks have to adapt to accommodate this prospect? And if this sort of mental-state-sharing might already obtain in some cases, how should this possibility impact our moral thinking? This question turns out to be extremely challenging, because different examples generate different intuitions: If two subjects share very few (...) mental states, then it seems that we should count the value of those states twice, but if they share very many mental states, then it seems that we should count the value of those statesonce. We suggest that these conflicting intuitions can be reconciled if the mental states that matter for welfare have a holistic character, in a way that is independently plausible. We close by drawing tentative conclusions about how we ought to think about the moral significance of shared mental states. (shrink)