If we were to connect two individuals’ brains together, how would this affect the individuals’ conscious experiences? In particular, it is possible for two people to share any of their conscious experiences; to simultaneously enjoy some token experiences while remaining distinct subjects? The case of the Hogan twins—craniopagus conjoined twins whose brains are connected at the thalamus—seems to show that this can happen. I argue that while practical empirical methods cannot tell us directly whether or not the twins share (...) conscious experiences, considerations about the locality of content processing in the brain entails that they most likely do so. (shrink)

Various cases of conjoined twinning have been presented as problems for the animalist view that we are animals. In some actual and possible cases of human dicephalus that have been discussed in the literature, it is arguable that there are two persons but only one human animal. It is also tempting to believe that there are two persons and one animal in possible instances of craniopagus parasiticus that have been described. Here it is argued that the animalist can admit (...) that these are cases in which human persons are not animals, without forfeiting the title “animalist.” It is also shown that this is not only an option but also a well-motivated and plausible option for the animalist. Seeing this requires getting clear on what the word “we” should be thought to include in the animalist's claim that we are animals. Here animalism is defended against twinning objections by figuring out how to view the scope of the animalist's identity claim. (shrink)

It is widely held that introspection-based self-ascriptions of mental states are immune to error through misidentification , relative to the first person pronoun. Many have taken such errors to be logically impossible, arguing that the immunity holds as an “absolute” necessity. Here I discuss an actual case of craniopagus twins—twins conjoined at the head and brain—as a means to arguing that such errors are logically possible and, for all we know, nomologically possible. An important feature of the example is (...) that it is one where a person may be said to be introspectively aware of a mental state that occurs outside of her own mind. Implications are discussed for views of the relation between introspection and mental state ownership, and between introspection and epistemic criteria for the “mark of the mental.”. (shrink)

From a felt, introspective perspective, one can identify various kinds of unity amongst all of one’s experiential parts. Most fundamentally, all of the states you are experiencing right now seem to be phenomenally unified, or, felt together. This introspective datum may lead one to believe that where consciousness exists, it always has this structure: there is always a numerically singular subjective perspective on a unified experiential field. In this dissertation, I expose this intuition and subject it to critical scrutiny.