Arguing From First Principles and the NAP

I often have discussions with people about how society should behave and how it should be organized. Being a libertarian, almost everyone I talk to disagrees with me on a lot of things, even many other libertarians. Sometimes, this stems from the fact that I’ve missed something while considering whether a particular action violates the Non-Aggression Principle, or NAP. But usually, it’s because the people I’m having the discussion with don’t argue from first principles at all.
The most common argument I find for this or against that is the utilitarian argument. The argument is usually something along the lines of this or that action will lead to either benefits or negative consequences for some person or group of people. The problem with that is that we have to decide who is going to benefit. Then the question becomes; who decides where the benefits are distributed? This line of thinking is usually directed at the “greatest good for the greatest number of people.” But there is still the arbitrary nature of deciding what that greatest good actually is.
The fact of the matter is that nobody actually knows. No person is close enough to omniscience to decide what actually is of benefit to the most people in a society. I like to adhere to a first principle like the Non-Aggression Principle, or NAP, for this very reason, because I don't know what's good for other people, only they do. I like it specifically because it is not arbitrary in nature. All I have to ask myself about an action is; is this action involving the initiation of aggression or force by one person or group of people against another person or group of people? If the answer is yes, I don’t accept that type of behavior. I also like it specifically because it’s how I want to be treated. I don’t want people attacking me for no reason, and I extend that preference to everyone else in society so as to avoid hypocrisy.
Now as I said in the introductory paragraph of this post, sometimes mistakes can be made when using first principles. That doesn’t change the fact that it’s much easier to know the difference between right and wrong in those murky “gray areas” that challenge so many people when deciding what civilized behavior is. I believe that all of our lives will be much easier to live as more people accept this line of thinking and behave accordingly. So please, don’t make the mistake of making arguments based on arbitrary criteria. Argue from first principles and you’ll have a much easier time, and a much more iron-clad case to make.