This article explores the relation between how scientific knowledge is created and the reasoning involved in learning content with understanding. Although an asserted parallel between these underpins reform, little is actually known about this relation. This article offers a model of this relation that draws coherent connections between the science studies literature, which suggests ways of conceiving how scientific knowledge is created; and sociocultural learning theory, which suggests ways of conceiving scientific reasoning. This model highlights a dialectic between construction and critique of claims in both scientific reasoning and practice. A “grasp” of scientific practice as such is instrumental to learning because informational content of scientific knowledge lies not only on the level of facts, but also on the levels of methods and values, and coordinating information across these levels is crucial for understanding. In contrast to prevailing constructivist ideas that highlight student authority to construct knowledge as scientists do, this model emphasizes the importance of knowing how to hold claims accountable. Thus, the ideal vision of students making their own sense of content is superceded by a more defensible ideal vision of students learning how to make scientific sense of content. © 2008 Wiley Periodicals, Inc. Sci Ed92:404–423, 2008