Uniformitarianism Re-Examined, or the Present is the Key to the Past, Except When It Isn’t (And Even Then It Kind of Is)

Abstract Perhaps no term in the geological lexicon excites more passions than uniformitarianism, whose motto is “the present is the key to the past.” The term is controversial in part because it contains several meanings, which have been implicated in creating a situation of “semantic chaos” in the geological literature. Yet I argue that debates about uniformitarianism do not arise from a simple chaos of meanings. Instead, they arise from legitimate disagreements about substantive questions. This paper examines these questions and relates them to several “forms of understanding” pursued by researchers in geohistory.