The paper discusses the structure, applications, and plausibility of the much used parallel-case argument for workplace democracy. The argument rests on an analogy between firms and states according to which the justification of democracy in the state implies its justification in the workplace. The contribution of the paper is threefold. First, the argument is illustrated by applying it to two usual objections to workplace democracy, namely, that employees lack the expertise required to run a firm and that only capital suppliers should have a say over the governance of the firm. Second, the structure of the argument is unfolded. Third, two salient similarities between firms and states regarding their internal and external effects and the standing of their members are addressed in order to asses the potential and limits of the argument, as well as three relevant differences regarding the voluntariness of their membership, the narrowness of their goals, and the stiffness of the competition they face. After considering these similarities and differences, the paper contends that the the parallel-case argument provides a sound reason in favor of democracy in the workplace a reason, however, that needs to be importantly qualified and that is only pro tanto.