It remains to indicate some of the principal accessions to Smith’s scheme of political economy after he left Glasgow. The task has been made easy by Mr. Cannan. In the first place, the chapters on Wages, Profit, and Rent in the First Book, and on Taxation in the last, mark a wonderful development and improvement of the imperfect and rudimentary treatment accorded to these subjects in the Lectures. Then again, chapter ix. of Book IV. on the French economists and their agricultural system is entirely new. The system of the _économistes_ is described in that chapter as one which, with all its imperfections, was perhaps the nearest approximation to the truth that had yet been _published_ on the subject of political economy. We are told that its adherents, a pretty considerable sect, had done good service to their country by influencing in some measure the public administration in favour of agriculture. They all followed “implicitly and without any sensible variation the doctrine of Mr. Quesnai,” whose _Economical Table_ they regarded with extraordinary veneration, ranking it with writing and money as one of the three great inventions made by mankind. Quesnai’s _Table_ showed three sorts of expenses: Productive expenses, Expenses of revenue, and Sterile expenses, with “their source, their distribution, their effects, their reproduction, their relation to each other, to population, to agriculture, to manufactures, to commerce, and to the general riches of the nation.” In the _Wealth of Nations_ this idea is followed out and improved; for the author, having shown in his First Book how the average produce of labour is regulated by the skilled dexterity and judgment with which it is generally applied, shows in his Second that it is further regulated “by the proportion between the number of those who are employed in useful labour, and that of those who are not so employed.” It would be absurd to call him a plagiarist; it would be equally absurd to deny that the French School had opened his eyes to the necessity for analysing the distribution of wealth no less carefully than its production. As the division of labour came from the Greek, so the distribution of the annual produce of wealth into wages, profit, and rent, came from the French philosophers. And we cannot forget that Quesnai’s death alone prevented Smith from dedicating his book to the inventor of the Economic Table. Equally important from the standpoint of theory, and far more so from that of the legislator and statesman, are the chapters upon taxation. There the lectures, though they made a distinct advance upon Hume, were rudimentary. But modern ingenuity cannot improve upon the four practical maxims or canons of taxation:— 1. The subjects of every State should contribute in proportion to their respective abilities. 2. A tax should be certain, and not arbitrary. 3. A tax should be levied at the time and in the way most convenient to the taxpayer.