Teaching chemistry remains a profoundly challenging activity. This paper arises from reflection on the challenges of creating meaningful assessments. Herein a simple framework to assist in making more visible the different kinds of knowledge required for mastery of chemistry is described. Building from a realist foundation the purpose of this paper is to lay the intellectual scaffolding for the framework. By situating the framework theoretically, it is intended to highlight the value of engaging with philosophy for the project of knowledge (...) building in chemistry. Use of this framework has laid bare some significant limitations to the ways in which organic chemistry has been assessed. Making the visible to students aids in their engagement with knowledge and for a small minority has developed their understanding of science more generally. The framework provides a simple, easily usable tool for the evaluation of chemistry assessments. (shrink)