It is widely agreed that the principle of tolerance, which upholds “complete liberty with regard to the forms of language,” epitomizes Carnap's philosophical outlook. Reflecting on this principle, Carnap notes that a more adequate designation would have been “the principle of conventionality” (1942, p. 247), or “the principle of the conventionality of language forms” (1963, p. 55). It should be remembered that insofar as conventionalism is considered a philosophy, Carnap would have been reluctant to characterize himself as a conventionalist: “I want to emphasize that we are not a philosophical school and that we put forward no philosophical theses whatsoever” ( 1934, p. 21, emphasis in original). Accordingly, “between our view and any … traditional view there cannot be identity – but at most agreement with the logical components. For we pursue logical analysis, but no philosophy” (p. 29, emphasis in original). And yet, conventionality is at the heart of Carnap's thinking; so much so that, to a considerable extent, his work can be seen as a series of attempts to uncover the conventional aspects of knowledge and thereby bring to light the connection between the classic philosophical conundrums, such as the nature of a priori knowledge and the controversy over realism, and the conflation of truth and convention. It is telling that, while the principle of tolerance maintains that there are no rights and wrongs, no “morals,” in the conventional choice of the appropriate language for a given task, the language Carnap uses to express the implications of his principle is emotionally charged and has pronounced moral undertones.