LA THEORIE DES KICHESSES. 189 



when the price decreases, and vice versa : the qualification " in gene- 

 ral" being here introduced to exclude certain classes of commodities, 

 such for instance as articles of curiosity and vertu, where a consider- 

 able fall in the price might even annihilate the demand altogether : 

 if diamonds could be manufactured as cheaply as glass, no one would 

 buy a diamond ring. Such cases, however, may be neglected in the 

 general theory. The rate of this increase or decrease of the sale, in 

 consequence of the fall or rise of the price, is dependent on the par- 

 ticular commodity, and may be more or less rapid ; in most manufac- 

 tured products, the increase of sale would be more than doubled if the 

 price were to fall one half: in other cases, such as the necessaries of 

 life, fuel, bread, and the like, and in cases where the demand is a 

 necessity to a limited class of consumers, as in workmen's tools, 

 weapons of war, philosophical instruments, there might be a consider- 

 able fall in price without the demand being much affected at the 

 time. Although this law of the demand is thus unknown, we are not 

 thereby precluded from reasoning with regard to it, for by well 

 known processes of analysis, properties of a function may be dis- 

 covered when the function itself is undetermined. If we now consider 

 the gross produce of any particular commodity, that is, the quantity 

 sold multiplied by the price at which it is sold, it is clear that the 

 value of this produce may be made as small as we please by 

 diminishing the price sufficiently, for even if the commodity were 

 given away, the consumption would still be a limited quantity. 

 On the other hand, we can conceive a price so high as to put an end 

 to the sale altogether, so that this gross produce would again vanish ; 

 between these two points therefore, there must be some particular 

 price at which this same gross produce will have attained its greatest 

 value possible ; up to which point it has been increasing and after- 

 wards begins to diminish — in technical language, it admits of a 

 maximum value. This then is the one great lever with which Cour- 

 not is going to move the world of economics, and we shall now proceed 

 very briefly to indicate the manner in which he has used it. Clearly, 

 however, we are not able to plunge at once into the thick of the mar- 

 ket, and demand that the principle shall be applied immediately 

 to the first commodity we lay hold of ; many circumstances must be 

 first considered, and it will be wiser to begin with the simplest case 

 we can conceive, even if it be a wholly imaginary one, and then pro- 

 ceed step by step till we arrive at a stage which may be approximate- 

 ly level with the actual condition of things as we see them around 

 us. Not the least part of the merit of Cournot's treatise consists in 

 his admirably-graduated progress from the simple to the complicated, 



