Cases that reach the Supreme Court are ‘hard cases’ where the result is not clearly dictated by statute or precedent. To reach a decision in these cases, a judge must exercise discretion and the non-legal factors that influence discretion have been the subject of extensive debate. Theoretical and empirical studies examining the influences on judicial discretion have focused on demographic characteristics and facets of the judicial personality including political ideology and attitudes. Personal values are related to these factors and have been demonstrated to play a role in decision making. This thesis demonstrates a relationship between personal values and judicial decision making in the Supreme Court. This thesis translates theories and techniques used in psychological research to examine the role of personal values in judicial decision making. A novel method of assessment of value expression in judgments was developed. This method revealed a different pattern of values expressed in the majority and minority judgments of cases that divided the Supreme Court, demonstrating a relationship between values and judicial decisions (value: decision paradigm). This was confirmed by an empirical study of legal academics. Drawing on this novel method, a series of Supreme Court cases were analysed to develop a theory of discretion, division, uncertainty, and values, suggesting that the influence of values is mediated through largely subconscious instinctive responses in cases where the outcome is perceived as uncertain. The role of values has significant implications in the debates surrounding judicial diversity, which have centred on overt characteristics, how the judiciary are seen. The study of judicial values has revealed tacit diversity in the Supreme Court which is associated with judicial decision making. The value: decision paradigm provides a new framework to analyse judicial decision making, judicial division, and the exercise of judicial discretion and the subconscious influences on these processes.