best remembered for his essay ‘Ce qu’on voit et ce qu’on ne voit pas’ (‘That which is seen and that which is unseen’) pointing out with great polemical brilliance that if, for instance, Napoleon employs his soldiers digging ditches and filling them in again, the fact that the soldiers are earning and spending money is easy to see, but the loss of income and employment due to the taxation necessary for this expenditure is not seen. In effect therefore he invented the notion later known as the opportunity cost. A committed liberal, Bastiat extended the argument to oppose all forms of state intervention in the free economy, and was an important influence on the Austrian School.