A description of the jobs in a labor force, an "occupational" description of it, is an abstraction for describing the flow of concrete work that goes through one or more employing organizations; the flow of work proba­ bly changes at a higher speed than the system for abstracting a descrip­ tion of its occupations and jobs. A career system is an abstraction for describing the flow of workers through a system of occupations or jobs, and thus is doubly removed from the flow of work. The federal civil service, however, ties many of the incentives and much of the authority to the flow of work through the abstractions of its career system, and still more of them through its system of job descriptions. The same dependence of the connection between reward and performance on abstractions about jobs and careers characterizes most white-collar work in large organizations. The system of abstractions from the flow of work of the federal civil service, described here by Thomas A. DiPrete, is an institution, a set of valued social practices created in a long and complex historical process. The system is widely imitated, especially in American state and local governments, but also in the white-collar parts of many large private corporations and nonprofit organizations and to some degree by gov­ ernments abroad. DiPrete has done us a great service in studying the historical origins of this system of abstractions, especially of the career abstractions.