As economy emerged from the economic interactions of people, it had the effect of encouraging more rational, economic thinking among people. Thus, it is not that man is Homo economus, as economists think, but that free markets make us more likely to act in more economic-rational ways. Since we remain social mammals, we will never be rid of our social rules of behavior which constrain our rationalist behavior. The irony is that as markets made man more rational, we began to think that using reason would be the best way to transform the world, that it could be rationally ordered and organized. The result was the rise of ideas of economic planning based on a rationalist model, giving rise to various forms of socialism. The irony being that, without free markets, the pressure on people to think rationally is released, so that socialism leads us directly back to nonrationalist thinking, and the very foundations originally claimed for having a planned economy are undermined. Faced with this, those who fundamentally support socialism turned away from rationalism, leading to the rise of postmodernism. Thus did rationalism undermine itself, not knowing its origins.