Bacon was an extreme proponent of the inductive method of finding truths, e.g. by categorizing all available facts on a certain subject to ascertain the natural laws governing it. His contribution to the development of science was abstracting the method of experiment from the concrete problem to see its bearing and importance as a universal method of research. He advocated changing education to include studies of the natural world using observation, exact measurement, and experiments. His explanation of a rainbow as a result of natural laws was contrary to theological opinion that a rainbow was placed in the heavens to assure mankind that there was not to be another universal deluge. The making and selling of goods diverged e.g. as the cloth merchant severed from the tailor and the leather merchant severed from the butcher. These craftsmen formed themselves into guilds, which sought charters to require all craftsmen to belong to the guild of their craft, to have legal control of the craft work, and be able to expel any craftsman for disobedience. These guilds were composed of master craftsmen, their journeymen, and apprentices. These guilds determined the wages and working conditions of the craftsmen and petitioned the borough authorities for ordinances restraining trade, for instance by controlling the admission of outsiders to the craft, preventing foreigners from selling in the town except at fairs, limiting purchases of raw materials to suppliers within the town, forbidding night work, restricting the number of apprentices to each master craftsmen, and requiring a minimum number of years for apprenticeships. In return, these guilds assured quality control. In some boroughs, they did work for the town, such as maintaining certain defensive towers or walls of the town near their respective wards. In some boroughs, fines for infractions of these regulations were split between the guild and the government. In some towns, the merchant guilds attempted to directly regulate the craft guilds. Crafts fought each other. There was a street battle with much bloodshed between the goldsmiths and the parmenters and between the tailors and the cordwainers in 1267 in London. There was also a major fight between the goldsmiths and the tailors in 1268. The Parish Clerks' Company was chartered in 1233.