The principle of equality of moral agency is central to moral libertarianism, because the need to allow every single individual their equal share of moral agency underpins the moral case for liberty and liberalism. As I have previously illustrated, liberals are not the only people who allow some kind of liberty, but we are the only ones who insist that liberty be given equally to every individual, not excluding those in government. Traditional feudalism allowed kings and lords almost boundless liberty simply by inheritance, but that meant slaves and serfs did not have any moral agency over their own actions, i.e. they could not act upon their moral consciences in their lives, but rather had to obey the consciences of their lords. We liberals, and moral libertarians in particular, cannot support offering anyone the kind of liberty kings and lords once had, because that would include having moral agency over other people, which means taking away other people's fair share of moral agency. Instead, we strive for every adult to have an equal amount of moral agency, which must therefore mean that everyone has full moral agency over themselves, and only themselves. But why is this important? And what does the application of this principle look like in practice?
What Equality of Moral Agency Implies
I believe that the principle of equality of moral agency is the most important principle in political morality, because it is the only way of distributing liberty (which is one and the same as moral agency, liberty being from a political rights perspective and moral agency from a moralistic perspective) that is consistent with the fact that every human being has equal moral standing from birth, and the fact that all human beings are flawed in some ways (i.e. not perfect and not capable of knowing the absolute truth in every sense). Let's start with the equal moral standing part. In fact, the founding fathers of the United States were some of the first people to recognise this: in their words, everyone was created equal, and therefore everyone has certain inalienable rights. Inalienable is the keyword here: these rights cannot be rightfully taken away by any action of any external authority, whether the authority comes from hereditary privilege or from collective mandate. Any action that compromises these inalienable rights are morally illegitimate. To believe that every human being is born equal morally requires that liberty (and hence moral agency) is distributed equally; in other words, a failure to distribute liberty equally is morally inexcusable, unless you happen to believe that people are not born equal. Now, let's look at the fact that all human beings are flawed. Because all human beings are flawed, nobody can certainly make the right decisions every single time. To allow one human being to make moral decisions for another against their will therefore potentially means forcing someone to commit a moral wrong even while knowing it is wrong. Furthermore, allowing those in power to make moral decisions for everyone else means that, when the leader of a country doesn't get it right, the whole country commits a moral wrong. The worst example of this in all human history would be the Holocaust.
Mussolini, the Father of Fascism: He Who Does Not Believe in Equality of Humans
Now, let's look at what happens when the principle of equality of moral agency is not respected. Mussolini, the father of fascism, was a classic example of a man who did not believe in the equality of moral agency. According to Mussolini, all the individual wills of the Italian people had to be moulded into one, and in practice that meant he had all the moral agency in the whole of Italy and his people had none. This was consistent with his belief that he was some kind of superman who could do no wrong, as captured by the slogan 'Mussolini is always right'. As Mussolini thought that he was not flawed and always made the right decisions, he believed he deserved moral agency over his people because he would always make the right decisions while his people may not. But of course, this was pure hubris on his part, as in reality he was one of the most immoral human beings who ever lived, and the ideology he invented brought endless misery to countless numbers of people. To disrespect the principle of equality of moral agency, to think that one can make a better decision and hence should have moral agency over other people, is to have at least some of Mussolini's hubris. While most people who believe in forcing their morality down other people's throats are nowhere as evil as Mussolini, their hubris is just as morally unsound.
Others who Disrespect the Equality of Moral Agency: Too close to Mussolini for comfort
The most classic case of Mussolini-style moral hubris is the kind of people who think they are carrying out God's Will, and hence have the authority to do anything in their 'mission'. Since they believe their ideas and actions necessarily reflect God's Will and hence the absolute truth, they believe there is no need to allow their human beings equal moral agency. This idea is most often associated with fundamentalist religious militants, who have caused tragedy after tragedy, who have committed utmost acts of evil while believing that they were carrying out God's Will. However, similar themes can be found in some sections of the religious right in the mainstream politics in many countries, who often self-righteously attempt to frustrate democratic mandates for liberal reforms because they think they are acting in God's Will. Thinking that one's beliefs in any area is certainly in line with God's Will is the same as thinking that one's beliefs, in that area at least, is 'always right'. This pattern of thinking leads straight to Mussolini-style hubris. On the other hand, a moral libertarian is allowed to have conservative viewpoints (otherwise it would defeat the point of moral libertarianism, right?), but they would need to make their case fairly and respectfully through the free market of ideas.
But it would be a folly to think that only those on the right are capable of such moral hubris. After all, Mussolini was left-wing when he was a young man. The left may not talk much in terms of God's Will, but they do talk a lot in terms of justice. Justice means the right thing to do, and is simply the secular equivalent of God's Will. Like how some of the political religious right think that their version of morality is always God's Will, an increasing number of leftists believe that their version of justice is always actual justice. When one starts to think this way, one essentially allows themselves the right to impose one's own version of justice on others, including those who do not believe in the same version of justice. For example, when authoritarian leftists believe that free speech leads to injustice, they insist that everyone practice safe speech (as they define it), and ideas that don't accord with their version of justice are met with actions of no-platforming, sometimes violent. Some moral libertarians may well share similar beliefs to these leftists in various areas, but out of respect of the equality of moral agency, would instead do their best to make their case in the free market of ideas, hoping to persuade other people to join their cause of action, while seriously dealing with the arguments thrown up by opponents. As a result of their morally unsound approach, the authoritarian leftists end up trying to impose upon everyone programs of 'justice' that even those who would supposedly benefit from don't want, like the kind of radical feminism that most women actually reject, or the kind of intersectional feminism that is actually GLIF (gatekeeper limited intersectional feminism, i.e. where intersectional oppressions only count if you have the correct political beliefs too). On the other hand, moral libertarians can continue to refine their ideas of justice through competition in the free market of ideas, gradually modifying what they offer as a result of feedback from people's lived realities, resulting in ideas that benefit as many people as possible.
Equality of Moral Agency: The Basics
So for those of us who decide that we don't want any part of Mussolini-style moral hubris, that we wish to respect and honour the equality of moral agency in every way, where do we start? First of all, we need to see our ideological opponents as having equal moral agency too. As long as they are not shoving their beliefs down other people's throats, to live and let live is our only option. No-platforming and safe speech are too fascistic to even be considered. Secondly, we need to learn to love and respect the free market of ideas. While it is a good thing to be strongly passionate about justice, we need to make our case in the free market of ideas, and treat our ideological opponents as equals in the process. We need to be open to feedback, especially in relation to people's actual lived experiences. This will make our ideological 'products' more responsive to the actual needs of individuals and families living in the real world, and make them more 'competitive' in the marketplace of ideas. Rather than seeing everything in us-vs-them (or 'class struggle') terms, we need to see the development of ideas of morality and justice as a continual process of refinement, which is facilitated by this free market of ideas, just like how the free market of consumer goods leads to the improvement of such goods over the years. Finally, we need to recognise that it is not up to any of us to determine subjectively whether each idea is progressive or 'regressive'. If an idea can thrive in the free market, it is by objective definition bringing new value to previously unserved populations and serving previously unmet needs, and is therefore progressive. If an idea is objectively regressive, i.e. it is worse than what is currently on offer in all respects and does not bring new value to anyone, it will not survive in the free market of ideas.