When judges are not interpreting, they’re creating, and to understand judicial creation one must understand first of all the concept of “priors.” Priors are what we bring to a new question before we’ve had a chance to do research on it. They are attitudes, presuppositions derived from upbringing, from training, from personal and career experience, from religion and national origin and character and ideology and politics. They are unavoidable tools of decision-making in nontechnical fields, such as law, which is both nontechnical and analytically weak, in the sense that there are no settled principles for resolving the most difficult and consequential legal controversies. The tools I am calling priors can in principle and sometimes in practice be overridden by evidence. But often they are impervious to evidence, being deeply embedded in what we are, and that is plainly true of judging — not in every case but in cases that can’t be resolved by interpretation or some other decision-making tool that everyone understands and uses in an identical way.
The priors that seem to exert the strongest influence on present-day Supreme Court justices are political ideology and attitudes toward religion.