 In  Section 4  it was noted that standardization involves choices among nontrivial alternatives, such as the choice among different thermometric fluids or among different ways of marking equal duration. These choices are nontrivial in the sense that they affect whether or not the same temperature (or time) intervals are deemed equal, and hence affect whether or not statements of natural law containing the term “temperature” (or “time”) come out true. Appealing to theory to decide which standard is more accurate would be circular, since the theory cannot be determinately applied to particulars prior to a choice of measurement standard. This circularity has been variously called the “problem of coordination” (van Fraassen 2008: Ch. 5) and the “problem of nomic measurement” (Chang 2004: Ch. 2). As already mentioned, conventionalists attempted to escape the circularity by positing a priori statements, known as “coordinative definitions”, which were supposed to link quantity-terms with specific measurement operations. A drawback of this solution is that it supposes that choices of measurement standard are arbitrary and static, whereas in actual practice measurement standards tend to be chosen based on empirical considerations and are eventually improved or replaced with standards that are deemed more accurate.