While Popper was writing the original German version of The Logic of Scientific Discovery during the early 1930s one of the issues on his mind was the rearguard action of Newtonians to resist the scandalous novelty of Einstein’s new theory. He used the term “conventionalism” to describe the attempt to retain an established theory against interloping novelties. This indicates that he was addressing the matter of paradigms (and the difficulty to challenge them) long before Kuhn entered the fray.
He saw that theories can be “immunized” against criticism in several ways – by means of ad hoc hypotheses, by shifting definitions, ignoring inconvenient observations and even by challenging the competence of rival investigators. Kuhn added the string of incommensurability to the conventionalist’s bow and another one is the charge of ideological or political bias.
These conventionalist strategies raised the issue of the social nature of science and the norms, traditions and conventions of the scientific community which he touched without elaboration in chapter 23 of The Open Society and Its Enemies (1945) and in the final sections of The Poverty of Historicism.
“Thus I was led to the idea of methodological rules and…of an approach which avoided the policy of immunizing our theories against refutation.”
The next step in the evolution of his ideas in 1932/33 came as he applied the critical approach to the test statements of the empirical basis and he recognised the conjectural and theoretical nature of observation statements. That in turn led to the recognition that all languages are theory-impregnated (the theory-dependence of observations) thus calling for a fundamental change in our perception of empiricism which hitherto had sought the solid foundations of knowledge in the data of observations or inputs from sensory organs.
“It also made me look upon the critical attitude as characteristic of the rational attitude; and it led me to see the significance of the argumentative (or critical) function of language; to the idea of deductive logic as the means of criticism…And it further led me to realize that only a formulated theory (rather than a believed theory) can be objective, and to the idea that it is this formulation or objectivity that makes criticism possible; and so to my theory of a ‘third world’.”
That evolution of thinking is sketched in the final section of chapter 2 in Objective Knnowledge (1970) moving from demarcation and induction to the rules of the game, to theories of language and the ideas of objective knowledge and the evolutionary link between language and critical thinking. As Jarvie demonstrated in The Republic of Science, all those themes were present in Popper’s first published work and it took a lifetime to draw out some of their implications.