To base the opposite truth is the mean of routing out a mistake.

Frédéric Bastiat
Complete Works, Volume 7, pages 131 to 134 (in French)
Mémorial bordelais, October 22nd, 1846

Frédéric Bastiat wrote three open letters to the traders of Le Havre in order to rally the French ship owners who partly benefited from the protectionist policy of the government  to the cause of the Association for Free-Trade. In this first letter, he mentions that the strength of liberty is so obvious that it is not necessary to demonstrate it. However, he admits that the public opinion is mistaken and that it therefore needs to be shown why.

The mistakes he delves on here is the belief that imports are not the fruit of national labour. However, due to the fact that services are exchanged against services, it is obvious that restrictions to international trade are also restrictions on national labour while imported foreign production does not destroy labour on a macroeconomic level. This is the point in today’s quote which is of a more universal reach, manifesting the “scientific” approach of Frédéric Bastiat’s reasoning.