Although expertise has a starring role in administrative law, there has been a surprisingly impoverished understanding of expertise and its role in the rulemaking process. The failure to understand expertise, which this article explains is more complex and multifaceted that generally understood, is problematic because understandings of expert public administration influence administrative law institutions and practices, and conversely these legal developments condition the creation and use of expert knowledge in public administration. This Article contends that a more complete understanding of expertise indicates how it is possible to have a more workable, and yet accountable, administrative process.More specifically, the article explains how the limited and sometimes misleading understanding of expertise has led to a “rational-instrumental” (RI) accountability paradigm, which distrusts agency expertise and seeks to narrow the policy space in which agency expertise can operate. A more accurate and complete understanding of expertise supports “deliberative-constitutive” (DC) accountability, which has the potential to increase agency effectiveness and still reconcile the administrative state with our constitutional democracy.