Locke’s theory on personal identity relies heavily on the matter of psychological continuity. He believes that the criteria for a human being and the criteria of a person are different (Study Guide, pg165). The criteria for a human being rely on the structural continuity of the being whereas the criteria for personal identity are the individual’s psychological continuity and his ability to withhold memory. The continuation of memory plays a vital part in Locke’s theory as, he believes that a person’s identity is shaped by the memories he has of himself (Study guide, pg166).

However, Butler and Reid objected certain aspects of Locke’s theory. In which, Butler stated that Locke’s theory was circular as, he had failed to notice that the relation of memory presupposes the notion of personal identity (Study Guide, pg167). Butler does not state that Locke’s theory of personal identity is wrong, however he is simply stating that Locke’s theory of memory cannot be a criteria for identity as it is causing a circular problem. This is because, if an individual identifies himself based on his memories, then memory and the individual would be the same thing. Hence, this in turn raises the question as to who holds the memory. Therefore, Butler believes that even though Locke’s theory may be right, the memory theory should not be a criterion of personal identity.

Reid also raised an objection with Locke’s theory whereby he believes that memory is neither necessary nor sufficient for personal identity. He stated that an individual’s past memory does not identify an individual’s identity but instead only reminds an individual of his past (Study Guide, pg166). Furthermore, memory is not a necessary criterion as an individual could have done something in the past that they no longer remember or made up a memory that they did not do. Therefore, memory should not be criteria for personal identity as it neither necessary (transitive) nor symmetrical (Study Guide, 166).