Cogito, ergo sum A different approach is that 'I think, therefore I am' means 'my mind works by thinking'. Descartes is regarded as one of the ancestors of mental representation theorists. Descartes thought that persons are the same as souls. He thought that souls operate by thinking. According to Descartes, the essence of mind is (mental) thought.
Similar arguments appeared in Kripke's argument against materialism. According to Kripke, Descartes is not identical to Descartes' body. When Descartes is dead, the corpse of Descartes is not identical to him.
Descartes did several things by 'Cogito, ergo sum': He derived his existence from the statement. He defined the nature of 'self' or 'soul' or 'mind'.