Aragón, Acevedo-Díaz and García-Carmona study prospective biology teachers’ understanding of the Nature of Science (NOS). In my comment, I would first like to step back and ask what it is to understand something, i.e. the sciences. I will turn to a quasi-Wittgensteinian epistemological tradition and suggest that, contrary to our habit to associate meaning with definitions, to understand something is, in fact, to engage in the normative practices around it. To understand the sciences then, we don’t need some definition; we need to engage in their practices. I will then turn to NOS research and suggest that NOS terminology, as well as certain NOS teaching practices, often fail to address two seemingly opposite mentalities, both of which prohibit understanding the sciences: scientism, i.e. the implication that there is in fact a definition of science; and relativism, i.e. the implication that, lacking a definition, science is a meaningless term. Both these mentalities could be challenged if NOS incorporated a quasi-Wittgensteinian account of what it is to understand something. In the last part of the paper, I will highlight some promising aspects of NOS research. To be specific, Aragón, Acevedo-Díaz and García-Carmona use the historical case of Semmelweis and childbed fever as a trigger to highlight certain elements of NOS and then facilitate reflective dialogue. Indeed, reflection over particular cases seems to be a promising way to understand the sciences; as a quasi-Wittgensteinian approach would suggest, it allows people to engage in the normative practices of scientific research. In the end, NOS researchers could benefit from such an epistemological account of understanding: avoid misconceptions such as scientism and relativism, as well as provide a strong theoretical background for their recommendations.