The question arises whether this invisible hand always works properly. Most individuals base their behaviour on a cost/benefit analysis of their own. Even an individual who tries to take the general interest into account has no inkling of the true costs and benefits of his decisions for society as a whole. In addition, individuals often base their decisions on less rational considerations as well.
Take, for instance, investor behaviour, such as the herd instinct on the stock exchanges. This can be explained by the theory of cognitive dissonance: investors filter information to justify earlier investment decisions. Economic textbooks often cite environmental pollution as an example of an area where the invisible hand does not work as it should.