There are various versions of anarchism. One relatively popular idea is that government should be replaced by competing protective agencies which define and defend rights and enforce justice for their paying customers. There are various alleged reasons offered for why this arrangement is better than a governmental monopoly on legal retaliatory use of physical force. The actual reasons for why one would support this idea can be discovered by observing what the idea's implementation would mean in practice.
John and Bob are decent people who ordinarily agree on most issues. John has a sexual relationship with Bob's teenage daughter, which he defends on the grounds that she is capable of deciding on this matter on her own. Bob believes that John should be punished because he manipulated a child into acting in a self-destructive way. How are Bob and John to resolve this dispute?
In a governmental system, John and Bob would appeal to the courts, who would resolve the dispute according to law. In an anarchistic system, if John and Bob belong to the same protective agency, they would have to utilize that protective agency's equivalent of a court. The issue becomes interesting if Bob and John belong to different protective agencies.
An agency's ability to protect its clients and enforce its clients' perception of justice is necessary to the agency's continued existence (since agencies which cannot do that do not receive many customers). Bob's protective agency must bring John (whom it perceives to be guilty) to justice (if it wants to survive). John's protective agency must protect John (whom it perceives to be innocent) from the initialization of force on the part of Bob's protective agency (if it wants to survive).
It's possible that the two protective agencies have previously established a method for resolving these sorts of disputes, and that they appeal to that method now. That's analogous and identical in result to the application of law by a court, so it provides no advantages over the governmental solution of the problem.
But, if Bob's and John's protective agencies have no previously established method for resolving disputes (and if they fail to make one now), the only recourse left to them is physical force. Bob's protective agency must destroy John's protective agency (which is protecting a criminal) while John's protective agency must destroy Bob's protective agency (which is initializing the use of physical force against an innocent).
The only two ways of resolving disputes between men are:
- An appeal to some objective way of solving disputes such as law or an impartial judge.
- Brute physical force.
Anarchism introduces brute physical force as a viable method of resolving disputes. In a governmental society, if Bob were to physically assault John, Bob would be held accountable by the government and would be treated as a criminal. In an anarchy, there is no entity which holds protective agencies accountable, and so Bob's protective agency is free to act against John's without fear of retaliation. Further, since in an anarchy the acting entities wouldn't be merely John and Bob but John's and Bob's protective agencies which consist of many people, the use of physical force would entail more death and destruction than John and Bob's dispute ever could in a governmental society.
What makes government a necessity is the need of honest people to resolve honest disputes by means other than physical force. A government is properly an entity which holds a monopoly on the legal use of retaliatory force, thus forcing people to resolve their disputes via impartial, objective laws. The solution to the problem of a government which initiates the use of force against its citizens is not discarding government as such, but finding ways to limit its power. This is the function of documents such as the United States Constitution.