What philosophical thesis do you think it most important to combat? > That selfishness is more rational than benevolence.But who puts forward this thesis he wants to combat? It seems like a reference to Adam Smith's famous suggestion that:
It is not from the benevolence of the butcher, the brewer, or the baker, that we can expect our dinner, but from their regard to their own interest.This is a widely misunderstood passage. It does not say "It ought not to be from the benevolence...", nor does it say "It would be less rational were it to be from the benevolence...". It says, quite simple, "It is not from the benevolence". This is not a recommendation, nor approval, nor a comment on rationality. It is an observation of fact.
People behave self-interestedly. They just do. They do in every type of social, economic or political system. Self-interest varies, it isn't always economic (status, for example, can be important and can work counter to economic self-interest), it isn't the only factor in human behaviour, but it is always a motivational force in people. And it happens to be the main reason why the butcher bothers to go to work.
Moreover, there's no suggestion in this passage that the tradesmen cannot or do not behave benevolently. It simply says that they don't go to work out of benevolence.
People - like me - who feel Smith was right in this passage are not trying to combat benevolence or advocate selfishness. We're simply observing that, in the human economy as in the natural world, lots of small acts of self-interest combine to form a rich and robust ecosystem.