  The doctrine of theory-ladenness is perhaps best appreciated when it is viewed against the background of the positivist tradition to which it was in large part a reaction. For the positivists, evidence was both epistemically and semantically prior to theory. Moreover, central to the positivist conception of science as a paradigm of rationality and objectivity is the idea that its disputes admitted of rational adjudication by appeal to evidence that could be appreciated by both sides. For these reasons, the positivists often insisted that the fundamental units of evidential significance—observation statements or ‘protocol sentences’—should employ only vocabulary that is within the idiolect of any minimally competent speaker of the relevant language.  Ideally then, observation statements should be comprehensible to and verifiable by individuals who possess no specialized knowledge or terminological sophistication. Thus, Carnap recommended ‘blue’ and ‘hard’ as exemplary predicates for observation  sentences.[33]  As against this, Hanson insisted that