One of the factors which accelerated this movement was a curious combination of high prices fixed by the economic law of supply and demand and low wages fixed by the ancient law of custom. It must be remembered that at this time the science of political economy did not exist. People did not know the laws which govern business and control prices and wages. They ignorantly supposed, as some persons still suppose, that these things may be governed by statute, being entirely unaware of the fact that they are really the product of causes for the most part beyond human control. In the early Middle Ages wages and prices were fixed on a basis of custom. The three centuries which formed the golden age of the guilds were a period of very slight industrial changes. There were no great changes in population. There was no colonizing, with the consequent opening of new markets. There were no modern inventions. There was no particular change in the amount of gold and silver in circulation. Consequently the law of supply and demand made itself felt so little through variations in prices and in wages that it was entirely neglected. It became the custom to pay a certain amount for each commodity, and especially to pay a fixed rate of wages in certain occupations. Nobody thought of paying less or of asking more than this customary sum. In case anybody did attempt any modification of this sort he was promptly checked by law. Attempts were also frequently made to prevent by law variations in prices. This condition of things was completely upset by the changes which took place about the time of the discovery of America. One of the immediate results of the opening up of the mines and treasure hoards of Mexico and Central and South America, with the consequent enormous increases in the amount of gold and silver in circulation, was a rise in general prices of about 100 per cent or, to put it differently, a cutting in two of the value of gold and silver. Gold and silver are just like other commodities. When the amount of gold in a given market is doubled its value is halved; that is to say, you have to pay twice as much for whatever you want to buy.