But the chaining of the individual to his commune was not sufficient unless his paying power was maintained. The same motives that impelled men to evade their fiscal duties by change of domicile, would make them idle and sullen paupers in the places where they were forced to remain. It was a part of the state system which the Severan emperors introduced to make the paying power of the citizen certain by means of the compulsory guilds.[390] These latter were natural outgrowths of former voluntary associations. The formation of guilds of laborers, either free or consisting partly of freemen and slave laborers, was as old as the state itself. The evident superiority of training which such groups insured alone justified them. From time to time certain privileges and exemptions were conferred upon them—always in return for definite state functions[391] which they took upon themselves as well as the industrial functions which were their reason for existence. Indeed, in the municipal towns the _collegiati_, or members of these publicly sanctioned industrial guilds, formed an order of citizenship second only to that of the decurions, or municipal senate. While the various _collegia_ were at first voluntary associations, it is evident that the sons of members would tend to follow the callings of their fathers without statutory command to that effect. When, however, the dues of the corporation to the state became onerous, the voluntary choice of a calling might leave certain _collegia_ quite deserted. At what time this danger became so serious that special legislation was required, we do not know, but there is a vague and textually uncertain passage in the Life of Alexander Severus, in the _Historia Augusta_, which indicates that a reorganization of the trade-guilds was undertaken by that emperor. If it was so, the appearance soon afterwards of the compulsory guild in full development makes it likely that the compulsory principle was officially recognized or perhaps extended then.