That doesn&#x27;t nail it down though. This just reshuffles the terminology so that we&#x27;re talking about individuals taking self-interested actions. Then we can ask of this &quot;madness&quot;: Why do we live in a society where individuals have so little common interest with the collective good? The language of rational self-interested actors does not predict the structure of society, it just gives you a convenient way of talking about that structure at the level of individual humans.<p>In particular, it does not explain why people perceive their self interest the way they do and it does not explain how those perceptions change. It does not explain how people come to find common interest with others and does not explain how someone&#x27;s notion of self and notion of society commingle and interact. These things are the definitions that let you talk about rational behavior in the first place.<p>This is by no means a defect of the concept. A microscope is not defective just because it is not a telescope, but it is still just a microscope. If you magnify a festering wound enough, it ceases to look so gruesome.