With the benefit of current scientific knowledge, most people who think carefully about personhood identify the brain as the seat of consciousness, and will tend to assume that any procedure that leaves the brain intact will leave the person intact too. If a brain (or a head in this case) can receive a 'body transplant' though, some will find it natural to wonder whether other radical interventions in the nervous system are possible; for instance whether subdivisions of the brain can be successfully transplanted, and what the effects of that might be.

That kind of speculation in turn prompts questions about the consequences that physical changes in the brain might have for conceptions of personal identity. Thought experiments about teleportation — in which all the physical matter of a brain is replaced while preserving its structure and function — offer a template for thinking about these questions by allowing their scientific and ethical consequences to be examined in the most extreme cases. The most extreme cases may or may not be realisable, but legitimate conclusions can nevertheless be arrived at by thinking about them.

Many of the most influential thought experiments in science were never conceived with the belief that they could be carried out in reality; that is often why they were thought experiments rather than laboratory exercises. The purpose of thought experiments is typically to help extend the theoretical investigation of scientific and philosophical ideas into realms beyond the reach of current empirical methods. They are a tool for considering interesting questions where attempts to test them cannot be made; sometimes this helps to inform practical experimental work, and sometimes the thought experiment itself is sufficient to reach reliable conclusions, if the reasoning is rigorous, and the underlying theory is demonstrably valid in enough areas where verification is possible for its extension to be trusted.