Locke asks whether or not a man who is drunk and a man who is sober continues to be the same "person". This leads to the more practical question of whether or not it is right to punish a sober man for any wrongdoing he did while drunk, assuming the sober man has no recollection of his thoughts and actions while drunk. The discussion results from a broader objection to Locke’s views, stated in section 20: "Suppose I wholly lose the memory of some parts of my life, beyond a possibility of retrieving them, so that perhaps I shall never be conscious of them again; yet am I not the same person that did those actions, had those thoughts that I once was conscious of though I have now forgotten them." (section 20 lines 1-6) In other words, are there not cases where personal identity persists, despite loss of memory? Moreover, would it really be better to base punishment solely on an identity based on memory? It seems strange to say that if a man gets drunk, he ceases to be that same person, and therefore is not responsible for his actions.

If Locke is to argue consistently with his hitherto discussed affirmations on personal identity, and he does, he must respond by saying that in such cases of total memory loss, there are actually two "persons" involved; as a result, he should and does say that the sober man should not be held responsible for his actions while drunk. This response depends first, on Lockes pronouncement in section 18 that "In...personal identity is founded all the right and justice of reward," and, second, on Locke’s central definitions of "person" and "man", and the implications this disctinction has on his ideas of what constitutes personal identity.

Anyone who would state the objection as it is phrased in section 20, says Locke, is confused about the referent of the pronoun "I". The "I" refers consistently to one "man", but the objector makes the wrong conclusion that this means it also refers to the same "person". Locke says we hint at this distinction linguistically when we say that a man "is not himself or is beside himself" (section 20 line 18) In saying this, we are acknowledging that a man is not identical with his identity.

In section 21 Locke tries again to clarify the distinction, showing how the three possible ways of determining the identity of a single man each lead necessarily to the possibility of plural identities. These identities, he argues, can only be defined in terms of "consciousness". First, an individual man could be defined in terms of his immaterial soul. In this case, Locke sees it as obvious that one man can consist of more than one "person", since two human beings living at different times would manitain one identity, and since one has no recollection of the other’s thoughts and actions. Second, a man’s identity could be due to his being a particular animal, regardless of his soul. Or third, a man can be the indication of loul and animal together Both of these, says Locke, make it impossible for one man (Socrates, for example) to maintain one identity throughout his own life. Again, this shows that one man can be more than one person.

For Locke, the above argument shows that there is no definition of man which excludes the possibility of the same man being more than one "person". This leads Locke to the conclusion that it is nothing more than an imperfect justice system which leads us to hold responsible and punish one "person" for what are in fact another "person’s" actions. A sober man is punished for acts commited when drunk, just as a man who is awake is punished for acts committed while sleep walking. Accroding to Locke, this is only because we have no way of proving that they are not the ame persons. Since we have no way of examining a man’s consciousness, past or present, we must make the ungrounded leap from identity of man, which is clearly picked out, since it is based on material substance but should not be the object of punishment, to identity of person, which is the identity to which moral responsibility is tied, but since it is based on consciousness is impossible to concretely disengage from a particular man. In a more perfect world, argues Locke, a particular sober man would not be punished for what he did while drunk.

Locke’s argument against the established means of selecting who should and should not be punished seems consistent with his views on personal identity. However, these views seem to neglect an important issue that would affect the issue of punishment. By defining consciousness, and therefore personal identity, solely in terms of awareness of past action, he fails to acknowledge a person’s possible awareness of the effects a present action can have on his future action. In other words, he bases the changing identity of the drunk man on his consciousness after he has sobered up and not at all on the same sober person’s decision to get drunk in the first place!