The Industrial Workers of the World (IWW) is a union of wage workers which was formed in Chicago in 1905 by militant unionists and their supporters due to anger over the conservatism, philosophy, and craft-based structure of the American Federation of Labor (AFL). Throughout the early part of the Twentieth century the philosophy and tactics of the Industrial Workers of the World were frequently in direct conflict with those of the American Federation of Labor (forerunner of the AFL-CIO) concerning the best ways to organize workers, and how to best improve the society in which they toiled. The AFL had one guiding principle—"pure and simple trade unionism", often summarized with the slogan "a fair day's pay for a fair day's work." The IWW embraced two guiding principles, fighting like the AFL for better wages, hours, and conditions, but also promoting an eventual, permanent solution to the problems of strikes, injunctions, bull pens, and union scabbing.