The assumption underlying parliamentary libraries is that Members have a fundamental need for high-quality information services to support their decision-making processes. This assumption can be questioned. The historical importance of the parliamentary library is assessed as a necessary myth projecting the modernity of the parliament and the legitimacy of its decisions. The standard narrative of parliamentary library history—that the evolving visions of parliamentary libraries are responses to the needs of Members—is not supported by the evidence. The origins of the service visions lie more in the copying of other services, responses to expert opinion, and wider professional developments. The library no longer signifies modernity and the myth has become a liability. An alternative paradigm of Members' information work is proposed, based on the concept of bounded rationality and, in particular, the work of Gigerenzer on "fast and frugal" decision making. Recent research confirms the importance of heuristics in decision making by Members. In this model of decision making, the parliamentary library makes its impact through improved environmental understanding and the framing of matters for decision, rather than the delivery of information at the point of decision. Giving easier access to information, and focusing on information for specialist Members, may have more impact on the quality of information actually used than efforts to improve product quality. A focus on the deployment of library competences in new areas of parliamentary information work is part of a vision for the future.