The Wealth of Nations by Part 5 Chapter 2 Page 95

cannot, consistently with his own interest, continue the employment. If he was taxed directly, therefore, in proportion to the whole profit, he would be obliged either to raise the rate of his profit, or to charge the tax upon the interest of money; that is, to pay less interest. If he raised the rate of his profit in proportion to the tax, the whole tax, though it might be advanced by him, would be finally paid by one or other of two different sets of people, according to the different ways in which he might employ the stock of which he had the management.

If he employed it as a farming stock in the cultivation of land, he could raise the rate of his profit only by retaining a greater portion, or, what comes to the same thing, the price of a greater portion of the produce of the land; and as this could be done only by a