According to Blasey, Kavanaugh was drunk when he assaulted her. While people sometimes try the drunk defense, it is usually not particularly effective. It is, however, a matter of philosophical interest, if only because John Locke considered the subject in his discussion of personal identity.
Locke argued, at length, that a person is their consciousness. Roughly put, memory is the basis of personal identity. Locke carefully distinguishes being the same person from being the same man. Being the same man for Locke involves being a collection of matter bound together by the same life; this could be looked at as biological rather than personal identity. When Locke considers the drunk defense, he notes that drunkenness could result in a person being unable to remember what was done. And if the person did not remember, then there would be no continuity of personal identity—thus, they would not be that person. Locke does note that human law, which must rely on the available facts, does not accept the drunk defense. After all, there is currently no way to establish or disprove a claim of metaphysical identity. As a practical matter, guilt goes along with being the same man (or woman) and this is not changed by a person being drunk. Since God is omniscient, He knows whether it was truly the same person or not and punishes accordingly. As such, unless God does a full memory restore on Judgment Day, people would not be morally accountable for what they permanently cannot remember because they would not be the person who did those actions. From a practical standpoint, Locke does note that the metaphysics of personal identity is not relevant—so the moral drunk defense would not work until Judgment Day (or until there is a means of determining metaphysical identity). Laying aside the metaphysics of personal identity, there are also important questions about moral agency and intoxication.
Intoxication, by its nature, impairs a person’s capacity to make judgments. As such, it is reasonable to consider that intoxication would impact a person’s agency. One controversial subject regarding agency is, of course, the matter of consent. The extreme end of the spectrum admits an easy and obvious answer to the question of consent: a person who is unconscious or almost completely incapacitated due to intoxication is incapable of granting consent. At the other end of the spectrum, a completely sober person (who is otherwise competent) can give consent. Between these two extremes lies a realm of controversy because it is not clear at what point exactly a person can no longer grant consent. It would, because of the line drawing fallacy (to reason that because one cannot draw an exact line between X and Y it follows there no way to distinguish between X and Y), be unreasonable to insist that precise boundary be drawn. Rather, we must settle on a somewhat fuzzy boundary and accept that their will be controversial cases. Fortunately, I do not even need to sketch the boundaries here, for the discussion will focus on cases in which one or more of the people involved are too intoxicated to consent.
If a person is too intoxicated to consent (and has not given prior permission), then engaging in sexual activity on them would be sexual assault (or rape). This is because the person’s intoxication has deprived them of the agency needed to grant consent. If it is agreed that intoxication can impair agency to a degree that consent is not possible, then it must be asked whether intoxication can impair agency to a degree that a person who engages in assault is not morally accountable for their actions.
One obvious point that might be brought up here is that a person incapacitated by intoxication would not be physically able to engage in assault while a person incapacitated by intoxication could still be assaulted. This is obviously true, so the matter hinges on whether there is a level at which a person is so intoxicated they cannot give consent, yet still capable of physically engaging in assault. If not, then the matter is settled. However, this does not seem to be the case—it does seem that there are levels of intoxication at which a person’s agency is so impaired that they cannot give consent, yet they are still physically capable of engaging in assault or rape. One can imagine someone who is stumbling drunk, cannot form complete sentences or thoughts and is yet capable of groping or engaging in sexual activity. As such, there does seem to be a matter to settle here.
If it is accepted that there is a level of intoxication at which a person lacks the agency to grant consent, yet is still physically capable of sexual assault, then the question is whether this lack of agency extends to accountability for sexual assault (or other evil actions). On the face of it, if a person lacks the agency to make judgments that allow them to consent, they also lack the agency to make judgments that would make them accountable for their actions. One way to look at the matter is that a lack of agency transforms a person into an object. While an object, like a falling tree, can do a lot of damage, it cannot be held accountable because it lacks the agency that grounds accountability. The obvious problem with this view is that while sufficiently intoxicated people cannot grant consent, it entails that sufficiently intoxicated people cannot be accountable for sexual assault.
One way to counter this view is to argue that an intoxicated person has their agency impaired rather than eliminated, so that an adult becomes analogous to a child (or animal). On this view, an impaired victim cannot grant consent because they lack the agency to do so. An attacker would, however, still retain enough agency to be accountable. To use an analogy, they would be like a dog that bites someone: the dog does not grasp concepts like consent but is still expected to know not to attack humans. As such, an intoxicated person would not be capable of granting consent but would still be accountable for attacking someone. The challenge here would be to argue that a person intoxicated to the degree that they cannot consent still retains enough agency to be accountable for engaging in non-consensual sexual activities.
A plausible approach is to argue that consent requires more agency and mental competence than recognizing assault and knowing that it is wrong. To use an analogy, an intoxicated person would be hard pressed to operate a complicated machine or solve a challenging logic or math problem, but they can still engage in basic tasks like opening another beer or working a remote control. So, expecting an intoxicated person to make judgments about giving their consent would be unreasonable, but expecting an intoxicated person to know better than to assault someone would be quite sensible.