In my current book project, Aphoristic Science: Ecology, Psychology, and Nineteenth-Century American Literature, I center this speculative science writing in the aphorism, a transatlantic style of writing with origins in the scientific texts of Hippocrates and Francis Bacon. Integrating scholarship in literature, philosophy, and science, I identify a particularly American stream of aphoristic thought permeating scientific prose in the nineteenth century. I focus on an interconnected group of American Transcendentalists and Pragmatists—Ralph Waldo Emerson, Henry David Thoreau, Emily Dickinson, William James, and W. E. B. Du Bois—who use the aphorism to engage readers in an unending process of interpretation. This “centrifugal” style encourages readers to continue a process of inquiry that spirals outward in new and creative directions. In defining the aphorism, I turn to the German-language tradition of Aphorismus (as distinct from Sentenz: the “sentences” or maxims, especially of the French moralists) to identify in the form an inherent evasiveness and ambiguity. Along the way, I draw on the extensive history of the aphorism to situate the form among science studies, affect theory, and a wide range of transnational theories of the aphorism.