Locke’s theory of personal identity: An explainer

Locke can present a bit of a challenge to VCE Philosophy students. Leaving aside the regular challenges associated with reading a philosophy text, Locke’s archaic writing style often leaves students stumped.

Below you will find Locke’s theory of personal identity explained in plain English. This explainer is not designed to replace a careful reading of the text. Instead, you should use this explainer to help guide your reading.

Locke’s theory of personal identity: Explained

For a printable PDF copy of this guide, please click here: Locke’s theory of personal identity PDF

Background: Distinguishing between man vs person

Locke begins by separating the concepts of substance, man, and person.

While many people conflate the terms ‘man’ and ‘person’, for Locke these terms refer to different things. A man is simply a member of the species homo-sapiens. A person, according to Locke, is a ‘rational, self-aware being capable of perceiving of themselves as existing over time’.

To draw out the distinction, consider a severely mentally disabled adult. This individual may be a man (they belong to the species homo-sapiens) but not a person (they lack the cognitive capacities necessary to conceive of themselves as existing over time).

In VCE Philosophy, Locke’s comments on persons are the most relevant: in short, we need to know how Locke answers the question “What makes a person the same person over time?”

Rejecting alternative theories

Locke outlines and rejects three possible candidates for what makes a person the same person over time.

Candidate 1: Same body

The theory: If A has the same physical form (body) over time, then A is the same person.

Locke’s rebuttal: If someone loses a body part, they are clearly still the same person. For example, suppose you have an awful hiking accident that requires your leg to be amputated. Though scarred, you would generally think you were the same person after the amputation as you were before the amputation – so having the same physical form cannot be the basis of personal identity.

Candidate 2: Same (overall) living system

The theory: A in 2018 is the same as A in 2016 if A is part of the same living system. To understand this theory, consider an old tree: though the form of the tree has changed throughout time (from a seed, to a sapling, to a full-grown tree), it is the same tree because the living system has continued throughout time.

Locke’s rebuttal: Locke argues that the sameness of a living organism is not sufficient for personal identity. To illustrate why, Locke offers his famous Prince and the Cobbler thought experiment.

In the Prince and the Cobbler thought experiment, Locke invites us to imagine that, overnight, a prince has all of his memories transferred to a cobbler’s body and the cobbler has all of his memories transferred to the prince’s body. When the cobbler-body wakes up, the consciousness ‘inside’ it thinks he’s a prince. When the prince-body wakes up, the consciousness inside it thinks he’s a cobbler.

Locke thinks that we would say that the prince is inhabiting the cobbler’s body and vice versa. If this is so, continuity of a living system is not sufficient for personal identity – because here, there has been a continuity of a living system (the bodies of the prince and the cobbler) but the identity has changed (the cobbler-living system now is the prince and vice versa).

Candidate 3: The soul

The theory: A in 2016 is the same at A in 2018 if they have the same soul.

Locke’s rebuttal: Locke gives two reasons why we should reject the soul as the basis for personal identity.

  1. The soul cannot be the basis for personal identity because we can imagine the same consciousness being transferred from one soul to another – for example, the prince’s consciousness could be transferred to the cobbler’s body and his soul.
  2. A soul might be shared between two or more persons, as in something like reincarnation.

Locke’s theory of personal identity: The main theory

Having rejected the three above theories of personal identity, Locke offers his own theory of personal identity. In VCE Philosophy Locke’s theory of personal identity is a key component of Area of Study 2, so it’s important you get a good understanding of the theory.

Locke argues that continuity of consciousness in the form of memory is what makes a person the same person over time. Consider the following example:

Angela in 2018 remembers graduating high school in 2017. According to Locke, then, Angela in 2018 is the same person as Angela in 2017 – because she remembers being Angela in 2017.

Objections & Locke’s responses

Locke considers two potential objections to his theory of personal identity.

Objection 1: Memory loss

The objection: Locke’s theory of personal identity cannot cope well with cases of memory loss. For example, imagine your grandmother has severe dementia and can no longer remember when she gave birth to your mother. According to Locke, because she cannot remember, your grandmother now is not the same person who gave birth to your mother then.

Locke’s response: Locke replies that this objection is not fatal – as he would consider your grandmother now and your grandmother then to be two different people.

Objection 2: The drunk man

The objection: According to Locke’s theory, a sober man cannot be considered the same person when drunk if he forgets what he has done while drunk. However, we usually treat the sober person as if they were the same as the drunk person, insofar as we feel it is appropriate to punish the sober person for the drunk person’s actions.

Locke’s response: Locke argues that, according to his theory, we should not punish the sober man for the drunk man’s actions. However, because we have no way of knowing what the sober man does and does not remember, we should apply the criteria of ‘same man’ (that is, is the physical form the same). If the sober man is the same as the drunk man, we may punish him accordingly.