Great quesion. Two approaches exist: psychological and philosophical. From a psychological point of view there is a sense of mind that involves an awareness of consciousness and our presence in society and our ability to control our own behavior. The philosophical approach is mind versus body. Do we really exist or are we just a figment of our imagination? What is real vs dream. Are we responsible or blind?
Autism. In short, having a theory of mind is to be able to reflect on the contents of one's own and others' minds." baron-cohen developed a term for lack of theory of mind that he called "mind blindness." it is used in autism. For many people with autism, it can be extraordinarily difficult to put oneself in another person's shoes in order to imagine what that other person might be thinking or feeling.