We as free creatures have the natural right to defense. Not only self-defense, but defense in general. If you are too weak to defend yourself, there are others who could help defend you. Anarchy isn't about chaos or survival of the fittest. Though it is closer to survival of the fittest than what we have now. Everyone should learn to defend themselves. That would be the smart thing to do. If you don't, then you aren't being responsible with your own life so you may suffer natural consequences for it. But In an anarchist society you wouldn't be alone. Other people or organizations could and would defend the weak. Whether it is a person, a group of people, charity police force, or free-market police force. People would tend to stick together as a group in a free society. It is a natural instinct for protection. Vigilante justice would prevail. Vigilante justice could scare people more than government justice today. I'm sure chaos would still exist. But even today we have chaos. At least anarchy is a philosophy of peace and freedom while government is about control which requires violence.