 Measurement is an integral part of modern science as well as of engineering, commerce, and daily life. Measurement is often considered a hallmark of the scientific enterprise and a privileged source of knowledge relative to qualitative modes of  inquiry.[1]  Despite its ubiquity and importance, there is little consensus among philosophers as to how to define measurement, what sorts of things are measurable, or which conditions make measurement possible. Most (but not all) contemporary authors agree that measurement is an activity that involves interaction with a concrete system with the aim of representing aspects of that system in abstract terms (e.g., in terms of classes, numbers, vectors etc.) But this characterization also fits various kinds of perceptual and linguistic activities that are not usually considered measurements, and is therefore too broad to count as a definition of measurement. Moreover, if “concrete” implies “real”, this characterization is also too narrow, as measurement often involves the representation of ideal systems such as the average household or an electron at complete rest.