Professor Andrew Manuel Crespo discusses his recent article, Probable Clause Pluralism. The constitutionality of a search or seizure typically depends on the connection between the target of that search or seizure and some allegation of illegal behavior—a connection assessed by asking whether the search or seizure is supported by probable cause. But as central as probable cause is to the Fourth Amendment, no one seems to know what it means or how it operates. The Supreme Court insists it is “not possible” to define the term, calling instead for the application of “common sense” to “the totality of the circumstances.” This article seeks to navigate, and resolve, this tension between doctrinal flexibility and structure. To do so, it urges a rejection of an often invoked—if not always followed—tenet of Supreme Court doctrine: probable cause unitarianism. That dominant idea holds that whatever probable cause means, it ought to entail the same basic analytic method and be judged by the same substantive standard from one case to another. But on close inspection, the Supreme Court’s jurisprudence contains seeds of an alternative, superior conception of probable cause, which this article terms probable cause pluralism. On this view, probable cause can comfortably encompass distinct analytic frameworks and substantive standards, each of which can be tailored to different Fourth Amendment events. From there, the article proposes a three-part framework for determining the constitutionality of a search or seizure, which can better equip scholars and jurists to reason through the cases to come and assess the cases that have come before.