 Finally, there is a model that holds that unity of conscious states consists in their ownership by a single subject, Bayne’s (2004) co-ownership. Is co-ownership meant to be necessary, or sufficient, or both? The idea that unified conscious experience must be had by a single subject could be trivially true, as it would be if the subject at a time is just defined as a set of unified contents. For the thesis to become interesting, advocates of it would have to offer a richer conception of the subject than that. On such a conception, the claim that experiences are had by the same subject would involve their attribution to the same extra-phenomenal substrate or bearer of experiences, one that can be individuated independently of what is to be found in experience, and thus independently of the notion of a unified field of conscious contents. Stated thus, the thesis would not be trivial and may well state a necessary condition of unified consciousness.