A presentation I delivered for my “Philosophy of Human Nature” course.
John Locke was a seventeenth century British philosopher of the empiricist school; though he is perhaps most famous for his work in political philosophy and his influence on American political thought in the eighteenth century, Locke also made some important contributions to metaphysics and the philosophy of mind in regards to the nature of personhood and personal identity. In book 2, chapter 27 of his Essay concerning Human Understanding, Locke attempts to address the philosophical problem of personal identity, that is, the question of what is necessary and sufficient to constitute a common personal identity over time despite changes enacted upon a person. In other words, what are the necessary and sufficient features of a thing that give it an identity over time?
Before dealing directly with the question of human personal identity, it is important to understand Locke’s distinction between things or objects and people. In his work, Locke explains the origin of identity for “vegetables,” “animals,” and the person. Objects of substance such as plants, animals, inanimate objects and human beings maintain their identity in a fundamentally different way from “the self” that constitutes the core of a person’s being. The identity of “vegetables” is maintained by the organization of the matter making them up. Objects of substance are, according to Locke, ultimately made up of “masses of matter.” These masses are made up of the substance out of which objects are formed. The objects themselves can be said to have identity in the sense that they maintain an organized structure over time. A rock, for instance, maintains its identity regardless of the substance because, even if all the matter comprising the rock were to be replaced, the rock would maintain its organization and structure, thereby maintaining its identity as that rock over time. This way of maintaining identity over time is common to all objects of substance, according to Locke, including human beings. The physical component of a man, the body, maintains its identity in the manner of an object, a plant, or an animal. The distinction, according to Locke, between these objects and a person is that a person is ultimately a thinking consciousness capable memory and of reflecting on itself and recognizing “the self” as continuous over time. This “thinking consciousness,” similar to Descartes’ “thinking thing,” is the necessary and sufficient feature which gives a person his individual identity. Regardless of the nature of the body or the soul, consciousness and the ability to reflect on the self are essential to personal identity. The ability to reflect and the ability to remember past experiences are necessary and sufficient features to show a common personal identity of the person.
The question of personal identity has been answered with three main suggestions about the nature of identity: the sameness of soul, the sameness of body, and the sameness of consciousness. The sameness of soul theory postulates that the soul is the feature which gives a person personal identity, the sameness of body says that the body serves this purpose. Locke’s argument about consciousness and the ability to reflect on the self point to the third idea about personal identity, the sameness of consciousness. On this issue, Locke walks the line between those who believe the body to be the feature supplying personal identity and those who believe it to be the soul. Locke’s argument for the importance of consciousness in this regard is based on the idea that the other two possibilities are fundamentally flawed in some way. Whereas consciousness is an essential feature of how the individual relates to himself and understands the “self” and personhood as abstract concepts, the body and the soul are less consistent components of the person. The body, for instance, without the ability to remember past events without the aid of the consciousness, could be inhabited by another consciousness with different memories and experiences, and the person would cease to have the same identity. The human being itself, that is the body, would remain the same, but the person would be fundamentally changed under these circumstances. If my consciousness were switched with that of Fr. McShane, the McShane body with my consciousness couldn’t be considered identical to him, and in the same way my body with his consciousness wouldn’t be identical to me. The person, Locke argues, is determined by the thinking component, regardless of body. A similar argument defeats the theory of sameness of the soul. Locke suggests that the soul, without a consciousness, could be transplanted into another body, and without a common consciousness to carry over the identity of the person, there could be no personal identity. This premise can be demonstrated in light of the idea of reincarnation. If a human being dies and its soul migrates into a cow, the soul serves to give the cow life, but it doesn’t retain the memories, experience, or distinct self-awareness of the original person. The cow is clearly not identical to the original person.
Locke essentially argues from the premise that there is a principle which is necessary and sufficient to provide personal identity. This principle must be common to the thing being examined over time, demonstrating that that thing is the same in one moment as in another. He then demonstrates what it is that is common to physical objects of substance, and what is common to the human being that gives those things their identity. Because, he argues, this identity fails to account for the thinking self, there must be another component that unites the identity of that aspect of man. Since the soul and the body fail, in this view, to account for continuing personal identity in memory, Locke points to consciousness as the source of identity for the person. Because memory and reflection on the self remain common to the person, these features, the consciousness, meet the criteria of that which is necessary and sufficient for identity, pointing to a separate personal identity in consciousness from the body. Locke’s argument appears to be valid, and it makes some reasonable criticisms of both those who believe in strict substance dualism and see the soul as the source of personal identity, and those who believe the body alone to be the source.
Ultimately, the question of personal identity is important to Locke because it involves a deeper moral and legal question, that is what actions are human beings accountable for based on changing personal identity? If, for instance, I am not the same person one moment as the next, then I could rob a bank and claim that the person who did it was not, in fact, fundamentally identical to me. Locke’s idea of the sameness of consciousness serves to tie me irrevocably to my past self and to make me responsible for my actions in the past. In its most basic sense, Locke’s argument is sound, and it achieves its intent of linking the person of the present to his past self and past actions.
While the argument remains valid and essentially sound, some questions about the exact nature of consciousness and identity in Locke’s view could easily be raised. The issue of memory in his conception of consciousness raises some questions about the relationship between a person in two stages of life when he cannot remember what occurred during an event in the past. If memory and the ability to reflect on the self are necessary and sufficient to show common identity between myself now and myself yesterday at lunch, what is the nature of that identity if I cannot remember what I ate for lunch yesterday? While intuitively it would seem I am clearly identical to myself yesterday, and I share a common personal identity with that person, because I don’t remember what I ate for lunch, my consciousness is fundamentally different and it seems I am a different person today than yesterday. This raises problems for Locke’s moral considerations because it brings into question the nature of moral and legal culpability in cases where the criminal can’t remember committing the crime. Locke answers this question, at least in regards to drunkenness, by drawing a distinction between the legal and moral responsibility of the individual. While he makes it clear that the individual should be legally responsible, because of the problem of the relationship between the drunken self and the sober self, ultimate moral responsibility is more questionable. In this sense, while Locke resolves the legal question, he fails to end this criticism of his theory. Memory, of the lack thereof, prevents me from being identical to myself during past events, and it calls into question the common personal identity between those selves.
Even in light of this criticism, Locke’s answer to the question of the persistence of personal identity provides an important insight into one possible unifying factor in identity. He essentially accomplishes his goal in demonstrating moral responsibility over time as part of identity over time. By proposing this theory about identity, he was one of the first to suggest what is now called the psychological answer to this philosophical question, which along with he biological answer, is one of the main positions taken by modern philosophers on the issue. Locke’s empirical view of the world led to this important contribution to philosophy.