There is hardly any effect that does not, in its turn, become a cause.
Today’s quote is the essential source of complexity facing the economist. Indeed, any action having an effect on the economy will change the situation that then becomes the starting point from which the next action will create an effect. The multiplicity of actions thus mixes with a multiplicity of situations that are permanently evolving, making it impossible to forecast accurately the effect of an action. The constructivist who thinks he can model society is therefore doomed to fail.
The chapter “Disturbing Factors” also shows that the issue facing the constructivist is that he does not believe that men act according to harmonious interests and that, as a consequence, he needs to force them or to deceive them so that they act according to his own vision of what their interest should be. This is presumptuous and it cannot work because there will be another constructivist who is even more arrogant than him, ready to review the modelisation of society according to another vision of what their interests are. Frédéric Bastiat believes that the interests of men are not antagonistic and that, as a consequence, letting them act according to their own interest leads to harmony. Man being subject to errors, this harmony will never be reached and society perfects itself through time.
This leads us to identify a second reason explaining why liberalism is preferable to constructivism, namely that the arrogant people who pretend to model society are also prone to error but if they have the authority to impose it on everybody else, the error will be much more damaging to society than an error any one individual can commit on his own (moreover, individual error generally creates the condition for its correction while errors made by government generally leads to expand the error even more).