Perspective

Is there one face or are there two faces in this picture? Two people can see something different and yet they are looking at the same thing.

Sometimes looking at different perspectives on the world can feel like you're looking at this picture, especially regarding different explanations for people's behaviour (as outlined below).

Social sciences point out that in any population of people some are really nice, some people are quite selfish, and most people are in the middle - they are nice if people are nice to them and mean if people are mean to them.

An explanation of this from an evolutionary point-of-view is as follows: if everyone in the group is very selfish then the group will self-destruct. So the best evolutionary 'strategy' is for people to be 'reciprocally nice', or 'conditionally nice'. That way, the group won't self-destruct, but people can secure their own self-interest and thus have a greater chance of effective reproduction. Naturally, evolution has selected for this. And, of course, extreme niceness is explained as either a random 'there has to be a bell curve and naturally people at the nice end', or there's some kind of evolutionary strategy going on there, as well.

Looking at the same evidence, there is also another, completely different explanation (albeit a bit more mysterious because of the 'free will' factor):

Suppose we have free will, and everyone can pick their moral character: really nice, really bad, or in between. On one hand, it makes rational sense for people to be selfish because then they can always pursue their interests. But on the other hand, we don't like being treated in that way, and so we feel bad about it because we feel we should 'Do unto others'. These are the considerations, and based on them, some people freely choose to value extreme niceness, extreme badness, or something in between.

As it so happens, the in between personality, 'conditional niceness', is the perfect compromise between securing our self-interest and 'Doing unto others' a fair bit. So, naturally, it's the most popular 'choice' when we pick and choose our characters. So in every population, through free will, you get a bell curve with some people at either extreme and most people somewhere in the middle, like with the first explanation, above.

As it so happens, this personality - the 'conditionally nice' - is also the most evolutionarily effective. But, actually, it comes through a process involving free will, rather than genetics.

So if you have free will + selfishness makes sense + we feel a moral obligation, then you can explain what we see, and if you use the idea of evolutionary strategies, then you can explain the data as well. So which is right?