This was the topic over which defenders of the consensus spent most of their energies. The aim of the philosophy of science, so they argued, is to exhibit and analyze this relation, but they disagreed among themselves radically as to the nature of this relation. Originally the hope was that one could "reduce" or translate theoretical statements into open ended sets of observation statements, but gradually this ideal was seen as unattainable. Later on, some, like the positivists Carnap and Reichenbach, were most anxious to develop a "logic of confirmation" according to which one could assess just how probably true any universal statement would be in the light of any particular body of empirical evidence. Others, like Popper, argued that empirical evidence could serve only a negative role, "falsifying" those hypotheses we ought to reject ("falsificationism"). According to this outlook what we ought to believe is those hypotheses subject to rigorous empirical testing which have not been refuted. Nevertheless, both the positivist "verificationist" program and its arch rival within the dominant consensus, the Popperian falsificationist program, both accepted some form of a "deductive-nomological model" (or "DN Model") of scientific explanation and a "hypothetico-deductive model" of the justification relation between evidence and theoretical statements.