Equality
Probably one of the hardest things for people to do is to admit that they are just like everyone else. We're strongly biased in favor of ourselves, that what we think is true and what we believe is right. That those who disagree with us must be mistaken. But, as a skeptic, I believe true knowledge is beyond our grasp. Whether or not there is any truth in the world, our imperfect senses prevent the certainty required for knowledge. I've written about my skepticism before, but there is another consequence of my skepticism - my belief in human equality.
When you're truly skeptic, you realize that your viewpoint is completely equivalent to everyone else's. There is no way to judge between the views of different people, so you must weight them equally. This is difficult to accept. We all have views that we are certain are correct, including strong moral positions. And we are often confronted with opposing views that we are just as certain are wrong. How could we ever consider the two equivalent?
I admit that for any human being, this is essentially impossible. Yet I believe that it is equally essential that we try. Thinking in terms of being right and wrong produces conflict and prevents people from seeing each other as equals. People often use the argument that they are "right" to justify their actions, especially when those actions have negative consequences for those who are "wrong." But, when there is a disagreement between two groups of people, they need to realize that they are looking in a mirror. Anything that one side does to the other, the other side will be justified in doing as well.
Therefore, the justification of our actions can never come from being "right." We should treat our enemies the way we treat our friends. However, this should not be mistaken as some sort of pacifism in the face of adversity or oppression. There are also times when we get into arguments or fights with our friends. To put it crudely, if someone takes a swing at me, I'm taking a swing back. But if I win, I'm not going to kick them once they're down. My point is that even when we have to defend ourselves, the way we do so should not depend on whom we're fighting.
Of course, many times when we do lose a fight, our enemy will kick us when we're down. So the temptation is strong to do the same when we come out on top. However, we need to realize that doing so would make us no different from our enemy, regardless of the justification. Treating people well, treating people equally, should not be contingent on them believing what we believe.
Equality is not possible in a world where people are certain of their beliefs, or at least use those beliefs as justification for treating others differently if they do not share those beliefs. The realization that we can never truly know anything, that we are fallible, is a necessary condition for any kind of equal society.