To begin with, recall that egoism is a relativist theory of ethics that maintains that right and wrong are relative to self-interest. Making self-interest the sole source of ethical value might seem a bit strange. After all, don’t we turn to ethics to understand how we should treat other people?
An egoist might try to sidestep this worry by saying that humans act out of self-interest anyway. If we only ever act out of self-interest, then we’re fooling ourselves about the importance of obligations to other people.
The problem with this is that, for every example of people naturally acting out of self-interest (e.g. securing their own survival by eating), there is an example of people naturally caring about others (e.g. having empathy for other people’s suffering).
If we do naturally act in both ways, then the egoist might still say that we are more likely to follow an ethic that we decide on ourselves than an ethic that’s forced on us.
Most of us can remember being told what we should or shouldn’t do when we were kids. What did we do when our parents or teachers laid down the law like this? A lot of the time we would rebel.
Even in adulthood we often resent being told what to do. So it makes sense that we are more likely to do something that we’ve decided on ourselves.
You should be careful with this argument. Making up our own minds doesn’t have to mean making up our minds to be selfish. Think of it this way: it’s true that you probably won’t give to charity just because someone else says so, but you could decide for yourself that you want to give to charity. As you can see, you can be self-determined whilst acting in the interests of others.
Another reason an egoist might give for being self-interested is that it’s good for society. In particular, they might point to historical or social development brought about by self-interested action.
They might also say that working in other people’s interests actually brings about bad results.
But you might worry that examples such as this are cherry-picked. Sure, you can point to times where self-interested action worked out well and other-interested action turned out badly. But perhaps we can also find counter-examples.
As you can see, it’s difficult to determine which kind of action really does bring about the best result. We would need some extremely broad and extensive empirical research to help us figure out which kind of action is best at promoting progress.
Like many ethical theories, egoism will sometimes give you evaluations that make sense to you, and sometimes ones that don’t. In other words, sometimes it will give intuitive results, and sometimes it will give counterintuitive results.
Egoism is also counterintuitive in that it says that we can only decide on what’s good relative to the person making the judgment. If something is good for me, then you can’t complain that it’s bad for someone else. In a similar way, if something is good for you, but bad for me, I can’t tell you not to do it.
This is troubling because most of us would want to say that things such as this shouldn't happen and that we have good reasons to believe this (i.e. it's not just an expression of our opinion, but ethically true).
Source: For ranking of countries on social progress see the "social progress index" http://bit.ly/2bE9UpI