Secondly, it has been generally agreed, that when the quantity of a commodity brought to market is neither more nor less than sufficient to supply all those who are able and willing to give the natural and necessary price for it, the demand may then, and then only, be said to be equal to the supply; because, if the quantity wanted by those who are able and willing to give the natural price exceed the supply, the demand is said to be greater than the supply, and the price rises above the ordinary costs of production; and if the quantity wanted by those who are able and willing to give the natural price fall short of the supply, the demand is said to be less than the supply, and the price falls below the ordinary costs of production. This is the language of Adam Smith, and of almost all writers on political economy, as well as the language of common conversation when such subjects are discussed. Indeed it is difficult to conceive in what other sense it could, with any propriety, be said, that the supply was equal to the demand, because in any other sense than this, the supply of a commodity might be said to be equal to the demand, whether it were selling at double or the half of its cost. Thirdly, it must be allowed, that according to the best authorities in books and conversation, what is meant by the glut of a particular commodity is such an abundant supply of it compared with the demand as to make its price fall below the costs of production; and what is meant by a _general_ glut, is such an abundance of a large mass of commodities of different kinds, as to make them all fall below the natural price, or the ordinary costs of production, without any proportionate rise of price in any other equally large mass of commodities. With these preliminary definitions, we may proceed to examine some of the arguments by which Mr. Mill endeavours to show that demand and supply are always equal in the aggregate; that an over supply of some commodities must always be balanced by a proportionate under supply of others; and that, therefore, a general glut is impossible.