 From this period, then, Carnap once again focused on scientific theories, and on theoretical languages as not fully reducible to empirical observation sentences. While he had given up the effort to reduce theories to observations, he remained preoccupied with the complementary problems of how a theory can be confirmed by observations, and how the empirical content of a theory can be determined. Both of these problems were articulated, and seen as interrelated, in “Testability and Meaning”, but thereafter they took separate paths. The first of these problems was central to Carnap’s preoccupation with inductive logic from about 1942, though he was never able to develop it to the point where it could be applied to the confirmation of theoretical sentences (as opposed to mere empirical generalizations). The second problem was the focus of significant attention to the nature of theoretical languages and the degree to which theories are constrained by evidence, as well as the problem how to identify the analytic and synthetic parts of a theoretical hypothesis or a theory, i.e., to distinguish what components of it come with the language framework in which it is expressed, and what components contain actual information about the world. See sections  8.1  and  8.3  below on Carnap’s further pursuit of both problems and his controversies and interactions with Popper, Hempel, and others on these issues. The supplement  The Reconstruction of Scientific Theories (Sections 3 and 4)  deals in more detail with Carnap’s distinction between observation language and theoretical language in science, and with Carnap’s reconstruction of scientific theories and theoretical terms by means of Ramsey sentences and related logical resources.