Earlier this year, an article in New York Magazine featured a story involving an eighteen-year-old woman who plans to marry and have children with her father. When the interviewer asked her to respond to those who might question her relationship, she offered the following reply:

I just don’t understand why I’m judged for being happy. We are two adults who brought each other out of dark places … When you are 18 you know what you want. You’re an adult under the law and you’re able to consent.

Her reasoning is typical of contemporary liberal approaches to sexual morality, which are usually justified by appealing to mutual consent. So long as an activity is performed in private between consenting adults, it is argued, there can be nothing inherently objectionable about what they do. Why? Because they have given their consent, and consent is what matters most when it comes to one’s decision to engage in sexual activity.

The implications of this position are far-reaching. Many have invoked the consent principle to argue for the permissibility of polyamory and consensual incest. Once we view the morality of sex as being determined only by mutual agreement, then it becomes very hard to make any principled distinctions about the shape of sexual relationships.

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When Consent Goes Wrong

There are a number of problems with this way of understanding sex. The most obvious problem with basing sexual morality on consent is that we can consent to things that are bad for us. Here we need only to think of those who deliberately cut themselves, desire the amputation of a healthy limb, or intentionally neglect their own health. These persons may have consented to engage in these activities, but their exercise of autonomy is nevertheless bad and self-destructive. So the mere fact that we may agree to do something does not show that what we are doing is morally permissible.

The defender of liberal sexual morality might respond by making a distinction between consent and informed consent. The self-harmer may choose to engage in these activities, but he does so without the full knowledge and understanding of the self-destructive effects that accompany them. If he really knew what he were about to do, then things might have turned out differently.

But this response is problematic for a number of reasons. If informed consent is just a matter of knowing the risks of one’s actions, then it is quite conceivable that someone may still freely choose to pursue self-destructive actions, having understood and accepted the risks. Yet there still seems to be something deeply wrong with a person who chooses to engage in self-destructive activities, even if he understands the risks of what he is doing.

Perhaps the claim is that someone who is aware of the risks would not act in such a way, thus saving the consent criterion from counterintuitive implications. But how do we know that? Why think that a sufficiently informed person would not choose to engage in self-destructive activities? If the answer is that a sufficiently informed person would know what is really good for him and thus act accordingly, then what is doing the justificatory work is no longer his consent, but his knowledge of some further fact that works to govern his decision-making.

Indeed, the appeal to some fact beyond mere consent ends up betraying the liberal position. Consent only has value insofar as it is used to make decisions based on knowledge of what is good for us. The issue then becomes one of determining what is in fact good for us as human beings. It is this issue that lies at the heart of contemporary debates over sexual morality and public policy. It is not about equal rights, but about what rights there are and the conception of human nature from which they flow. The value of consent lies not in the ability to make our own decisions, but in making the right decisions.

Why Consent Alone Is Inadequate

On a deeper level, the most important problem with liberal appeals to consent is that they misunderstand the very function of consent. To give consent is to give permission for someone to do something that he would otherwise have been forbidden to do. Consent works by delegating permissions from those who have them to those who do not. When one gives consent, he is handing over a “moral key,” so to speak.

This, of course, assumes that I have the pre-existing right to authorize some course of action. I cannot give permission for someone to do something if I am not authorized to grant it. I cannot, for instance, legitimately consent that my friend take my neighbor’s property, for I myself have no right to it. I may say that I am giving permission, but my consent is worthless, since it is not mine to give. My consent cannot confer a moral license to do something if I do not have that license myself. Thus, appealing to consent to justify some controversial sexual activity only works if the kind of sexual activity in question is already morally licit. If it is not, then consent cannot justify it.

The Harm Principle

Appeals to harm fall short in much the same way. It is sometimes said that since certain private sexual activities between consenting adults do not harm anyone, they are therefore morally permissible and should be legally allowed. This argument appeals to a version of John Stuart Mill’s famous harm principle. In a famous passage in On Liberty, Mill writes that the “only purpose for which power can be rightfully exercised over any member of a civilized community, against his will, is to prevent harm to others.”

The problem with this argument centers on the meaning of “harm.” Persons can be harmed physically, morally, spiritually, psychologically, culturally, educationally, financially, and in many other ways. A harm is simply a setback to any kind of flourishing, and persons flourish in a variety of ways. In a moral sense, every immoral action necessarily harms both the person and the community, for in acting immorally he acts against the moral order. If certain sexual acts are immoral, then they are necessarily harmful as well.

We cannot speak meaningfully of harm prevention without adopting a prior theory of what it means to flourish. As result, the state cannot be neutral when it comes to issues of consent, autonomy, liberty, and harm reduction. Since invoking these concepts presupposes some prior understanding of the good life, the state must inevitably adopt some comprehensive moral framework when it comes to regulating social life. The question then becomes: “Which framework should we adopt?”

This is a question that has been conveniently ignored by contemporary liberals, especially when it comes to the same-sex marriage debate. While natural law critics of same-sex marriage have argued for a comprehensive understanding of the nature of marriage, advocates of same-sex marriage sidestep the metaphysical question and instead appeal to the question-begging language of equal rights. But as we have seen, the debate is not about equal rights, but about the nature of marriage.

The Purpose of Freedom

Sexual liberalism’s misguided view of consent is a symptom of a deeper problem: we have forgotten what it means to be free. Our power of free choice, like the rest of our nature, has a purpose. The point of freedom is not to choose whatever we want, but to choose only those ends that are in accordance with our rational human nature. It is this exercise of freedom that gives rise to self-mastery. This classical understanding of freedom was best expressed by Samuel West, in a sermon delivered to the Massachusetts legislature in 1776:

The most perfect freedom consists in obeying the dictates of right reason, and submitting to natural law. When a man goes beyond or contrary to the law of nature and reason, he becomes the slave of base passions and vile lusts; he introduces confusion and disorder into society, and brings misery and destruction upon himself. This, therefore, cannot be called a state of freedom, but a state of the vilest slavery and the most dreadful bondage. The servants of sin and corruption are subjected to the worst kind of tyranny in the universe. Hence we conclude that where licentiousness begins, liberty ends.

We must not merely consider what a person wants but also what he should want. By valuing freedom as a good in itself, we have lost sight of what freedom is for. Not all choices are created equal. As West observes, we are most free when we use our freedom to perfect ourselves, and we perfect ourselves by making choices that respect the goods that are constitutive of our human nature. The “most perfect freedom,” in other words, consists of the pursuit of truth and the rejection of error. When choices are guided by emotion and passion instead of reason, the person is no longer in control. While one may feel liberated, he becomes a slave of the non-rational.

The purpose of freedom is to choose. But what should we choose? Just anything? What moral principles should constrain our choices? Once we grant that our choices should be constrained, we have given up a view of freedom in which the exercise of freedom is a good in itself.

We must first look to human nature and understand the goods that fulfill it. Only then can we really understand what it means to be free. Appeals to consent, autonomy, liberty, and harm all rest on moral assumptions that need to be justified. While conservatives have offered powerful defenses of their moral assumptions, this task has been ignored by defenders of liberal sexual morality.