141. This is Professor Sidgwick’s doctrine.[28] It has given great comfort to our protectionists because it is put forward by an Englishman and a Cambridge professor. It is offered under the “art” of political economy. It is a new thing; an _a priori_ art. The “may” in it deprives it of the character of a doctrine or dogma such as our less cultivated protectionists give us--“Protective taxes come out of the foreigner”--but it is not a maxim of art. It has the air of a very astute contrivance (see § 3), and is therefore very captivating to many people, and it is very difficult to dissect and to expose in a simple and popular way. It has therefore given great trouble and done great mischief. It is, however, a complete error. It is not possible in any way or in any degree to use duties so as to make the foreigner pay for protection. 142. Professor Sidgwick states the hypothetical instance which he sets up to prove by illustration that there “may” be such a case, as follows: “Suppose that a five per cent duty is imposed on foreign silks, and that, in consequence, after a certain interval, half the silks consumed are the product of native industry, and that the price of the whole has risen 2½ per cent. It is obvious that, under these circumstances, the other half, which comes from abroad, yields the state five per cent, while the tax levied from the consumers on the whole is only 2½ per cent; so that the nation, in the aggregate, is at this time losing nothing by protection, except the cost of collecting the tax, while a loss equivalent to the whole tax falls on the foreign producer.” 143. It is necessary, in the first place, to complete the hypothesis which is included in this case. Let us assume that the consumption of silk, when all was imported, was 100 yards and that the price was $1 per yard. Then the following points are taken for granted, although not stated in the case as it is put: (1) That the state needs $5 revenue; (2) that it has determined to get this out of _the consumers of silk_; (3) that the advance in price does not diminish the consumption; (4) that the tax forces a reduction of price for the silk in the whole outside market; (5) that the “_silk_” in question is the same thing after the tax is laid as before. Of these assumptions, 3, 4, and 5 are totally inadmissible, but, if they be admitted in the first instance, and if the doctrine of the case which is put be deduced, it is this: If the part imported multiplied by the tax is equal to the total consumption multiplied by the advance in price, the consumers can pay the latter in protection, for it is equal to the former, and the former, which is paid to the government by the foreigner, is what the consumers of silk must otherwise have paid.