When the great truths of Political Economy shall become generally known—when men shall be convinced that each person will sell with greater facility the more others gain; that they can only gain by means of labour, capital, or land; that the greater the number of producers the greater the number of consumers; that unproductive consumers are mere representatives of others, and can only consume by means of what others produce; that all nations are interested in the prosperity of each other, and in facilitating the means of communication; that capital or land, and even labour, can only be productive while it is respected as property, and that the poor but industrious man is interested in the defence of the property of the rich, and in maintaining good order, because their subversion may deprive him of the means of subsistence:—when these truths shall be generally known, it will be almost impossible to stir up nations or bodies of men against each other. This science therefore is eminently social, and by teaching that no men can injure others without injuring themselves, and that the advantages gained by others are productive of advantages to themselves, will probably effect what a less interested doctrine has not yet accomplished.

– Translator's preface to Letters to Mr. Malthus (1821) by Jean-Baptiste Say, pp. vi–vii

(The Mises Insitute has also made available J-B Say's Treatise on Political Economy.)