 This period also marks a return to the recognition that radical positivism of the “molecular” or Tractatus sort hardly does justice to actual science—so Carnap returns now to science as it actually is done rather than an idealized, purely factual science. This meant, once again, an acceptance that theoretical vocabulary needed to be accounted for in one’s conception of science. Another kind of concept characteristic of actually practiced science that gets special attention in “Testability and Meaning” is disposition concepts (e.g., “soluble” or “refrangible”; more on disposition concepts in the supplement  The Reconstruction of Scientific Theories (Section 2)).  Probabilistic concepts would soon come into focus as well as a significant preoccupation.