This chapter concerns itself with a deepening discussion on measurement in the form of two key questions. First, building upon previous chapters: what is it that risk-based resilience reasoning systems should, in fact, measure? Second, by starting to unpack what we have only heretofore referenced as statistical technique, how should this be measured? Beginning with the, industry-normative, probability and impact scaling, we quickly demonstrate how these are scientifically indefensible as currently used. Examining the properties of available alternatives, we specify a minimum set of criteria that should be used. We note that, even at the minima, these are more complex than the preferred measurement currencies at what might be considered their most sophisticated. We then examine in detail some of the known fallacies of judgement in four worked examples. These form a hierarchy of measurement tasks, starting with mean estimation and culminating in conditional probability. In each case we note, in line with the research, that the measurement required to validate the perceived utility of a resilience reasoning system lies at the upper band of complexity – a band that is a notorious snare for unwary practitioners without training. The whole question of measurement scaling, we feel, requires significant revision.