Lewis defends an account of the role of theoretical terms in scientific theories. Drawing on the work of Ramsey and Carnap, Lewis advocates the view that theoretical terms are implicitly defined by the scientific theories in which they figure; their meanings are to be characterized in functional terms, by reference to causal roles. According to Lewis, this understanding of theoretical terms (which would become influential in the development of functionalist theories of the mind) enables us to understand how one scientific theory may be reduced to another.
Keywords: bridge laws, Rudolf Carnap, causal role, functional definition, functionalism, holism, Frank Ramsey, reduction, scientific theory, theoretical terms