 The criterion of epistemic transparency  (Section 2.1)  encourages an exploration of our third interpretive option—the lack of reference to theories should be taken at face value. Developmental biology is organized primarily by stable, broad domains of problems that correspond to abstract representations of major ontogenetic processes (differentiation, pattern formation, growth, and morphogenesis;  Section 1.2).  Yet how do we interpret the “theoretical” aspects of developmental biology (e.g., positional information models of pattern formation) and the utilization of theories from other domains (e.g., biochemistry)? One way is to distinguish between theory-informed science—using theoretical knowledge—and theory-directed science—having a theory that directs inquiry and organizes knowledge (Waters 2007b); developmental biology is theory-informed but not theory-directed. Theories need not be wholly absent from developmental biology but—when present—they play roles very different from standard philosophical expectations. Developmental biology uses theoretical knowledge from biochemistry when appealing to morphogen gradients to explain how segments are established or chemical thermodynamics when invoking reaction–diffusion mechanisms to explain pigmentation patterns. It also uses theoretical knowledge derived from within developmental biology, such as positional information models. Different kinds of theory inform developmental biology, but these do not organize research—they are not necessary to structure the knowledge and direct investigative activities. Developmental biologists are not focused on confirming and extending the theory of reaction–diffusion mechanisms, nor are they typically organizing their research around positional  information.[6]  This theoretical knowledge is used in building explanations but does not provide rails of guidance for how to proceed in a research program. All sciences may use theoretical knowledge, but this is not the same as all sciences having a theory providing direction and organization.