Joseph Bizup's BEAM schema establishes a rhetorical approach to research writing pedagogy, articulating four distinct ways writers use sources: for background, exhibit, argument, and method. This article rechristens the framework I-BEAM, identifying a fifth category: instance source use, a constitutive function that establishes the need for the writer's argument. Instance source moves appear in numerous locations––introductions, textual asides, footnotes/endnotes, and epigraphs––and can situate the writing in both academic and popular contexts. Attention to this exigency move highlights the problem of authenticity in school-based writing and raises questions about sources formative to the writer but invisible to the reader.