This process of reasoning seems to imply that the revenues of the agricultural and industrial classes are not squeezable because they represent the indispensable minimum necessary for the expenses of production. This seems to be an anticipation of the notorious “iron law.” Turgot’s formula incisively stating this law, but containing no attempt at a justification, is known to most people.[104] Long before his day, however, it had been stated by Quesnay in terms no less pronounced, though perhaps not so well known. “It is useless to urge that wage-earners can pay the tax so levied upon them, by restricting consumption and depriving themselves of luxuries without thereby causing the burden to fall upon the classes who pay the wages. The rate of wages, and consequently the amount of comfort and luxury which wages can purchase, are fixed at the irreducible minimum by the action of the competition which prevails among them.” This is quite a characteristic trait.[105] The author of the “natural order,” without any hesitation, admits that the direct outcome of the establishment of that order would be to reduce the life of the wage-earners to a level of bare subsistence. It is also remarkable that in their study of the industrial classes wages should have claimed the exclusive attention of the Physiocrats. Profits even then were by no means unsqueezable, but curiously enough they failed to realise this. Voltaire’s rich banker would have proved embarrassing here. They would have had some difficulty in showing how a reduction of his extravagance could possibly have endangered production. But they might have replied that since he had so little difficulty in squeezing the 400,000 _livres_ out of his fellow-citizens he would not experience much more trouble in getting another 400,000 out of them and paying them over to the State. Another objection consists in the insufficiency of a single tax to meet all the needs of the State. “In some States it is said that a third, a half, or even three-fourths of the clear net revenue from all sources of production is insufficient to meet the demands of the Treasury, and consequently other forms of taxation are necessary.”[106]