The problem of epistemic or knowledge-related discretion arises whenever knowledge of what is commanded or prohibited by the constitution is unreliable. The unreliability of knowledge and the resulting discretion are important aspects in the balancing of constitutional rights. Robert Alexy has, in his Theory of Constitutional Rights, laid down an analysis of epistemic discretion that appears to raise a number of questions. These concerns include the relevance of empirical and normative knowledge in balancing, the function of reliability in the Weight Formula, and the correlation between epistemic discretion of the legislature and judicial review by a constitutional court. This article highlights some of the problematic issues and suggests several modifications of and completions to Alexy's analysis.