 From the Aufbau (see the supplement  Aufbau (Section 2)  on Carnap’s early structuralism) to his mature reconstruction of scientific theories (see the supplement  The Reconstruction of Scientific Theories (Section 6)  on Carnap’s later structuralism), Carnap sought to articulate an innovative type of conceptual or linguistic structuralism about science that is metaphysically neutral and which resembles modern versions of structuralism about mathematics: the cognitive content of what can be asserted precisely and meaningfully in science can be reconstructed as a structural constraint on empirical content, and one should aim at such structural reconstructions as they enhance the objectivity of science. While structural properties are expressed using logical concepts usually discussed in the context of deductive logic, Carnap’s later work on inductive logic considers probability measures that are logical or structural in the analogous sense, i.e., where probabilities remain invariant under isomorphisms. This “inductive structuralism” is discussed in supplement  Inductive Logic.