Mind Transplants

A popular idea in science fiction consists of a mind being transplanted to another person’s body. Some movies have also revolved around the idea of an adult mind functioning within an infant, or a dog.

Although these scenarios provide for humorous situations, are they really credible?

Suppose a screenwriter gives to you a screenplay, featuring a mind transfer to another body. If you prefer, you can take a real example, say, ‘Being John Malkovich’ or ‘Freaky Friday’ or ‘All of Me’

Taking the position of either a physicalist or a dualist, what scientific-philosophical advice would you give to someone who wanted to write a screenplay featuring such a scenario?