I have previous said that the act that creates government is the act that entrusts some people with the common good. But what is the common good? One way one might be an anarchist is to deny that there is a common good either in general or for governments. This is impossible because every group of people has a common good arising from what unifies those people.
The common good is not the good of the majority. It is perfectly possible for the majority to want something good, but for that good thing to be a special interest. For example, as Canada ages, the majority will want the needs of the elderly to be privileged. But it is not right to treat one group as better than another, even if that one group is in the majority. For another example, consider what would happen if the majority of people were between 18 and 30 years old. This group may wish to have their needs such as a university education or a new car satisfied by everyone. But this is clearly unfair. From this we can gain a principle: the common good does not intentionally benefit one group of people over another.
The common good must distinguish between what is good for individual people, and what is good for people as members of a group. It is because the people are members of a group that the common good applies to those people. An individual who is completely alone and isolated from society cannot have a common good. Having said that, most people are members of society simply by residing next to other people, being members of voluntary or partially voluntary groups and having relationships with other people.
In any group, the common good is the good that applies to a group in virtue of membership to that group. For a sports team, the common good of the sports team is what helps that sports team to be a good sports team. Sports teams are not the only groups that have a common good. In fact every single group has a common good. If it is possible to speak of a good or bad group in general, than that group has a common good. This means that if governments exist, then there is a common good for governments.
Since governments are formed from people without a further distinction, any good that arises must be a good common to humanity. It would be impossible for a distinction between good and bad government to be drawn unless something unified government generally. But as I have previously shown, there is no property that one government has and another lacks (assuming that historical acts are not properties). Governments exist because of a historical act that created them, but that act also created the country governed by the government. So the only commonality other than the country is the common humanity of citizens. Since the country cannot explain the common good that the government was entrusted with, that common good must be the common good of humanity.
This does not show what the nature of the common good is or how to determine what it is, but only that there must be such a thing. The only route to anarchism remaining is to declare that the common good need not be entrusted to some, but that voluntary and partially voluntary groups can manage the good common to humanity without a government doing so.