Ramsey sentences are formal logical reconstructions of theoretical propositions attempting to draw a line between science and metaphysics.
Ramsey sentences were introduced by the logical empiricist philosopher Rudolf Carnap.
Inside this framework, entities such as electrons or sound waves, and relations such as mass and force not only exist and have meaning but are "useful" to the scientists who work with them.
To accommodate such internal questions in a way that would justify their theoretical content empirically – and to do so while maintaining a distinction between analytic and synthetic propositions – Carnap set out to develop a systematized way to consolidate theory and empirical observation in a meaningful language formula.
Immediately, a problem arises: neither the German nor the English language naturally distinguish predicate terms on the basis of an observational categorization.
As Carnap admitted, "The line separating observable from non-observable is highly arbitrary."
But "hot" might take place at such a microlevel (e.g., the theoretical "heat" generated by the production of proteins in a eukaryotic cell) that it is virtually non-observable (at present).
Physicist-philosopher Moritz Schlick characterized the difference linguistically, as the difference between the German verbs "kennen" (knowing as being acquainted with a thing – perception) and "erkennen" (knowing as understanding a thing – even if non-observable).
The next step for Carnap was to connect these separate concepts by what he calls "correspondence rules" (C-rules), which are "mixed" sentences containing both T- and O-terms.
The resulting "Ramsey sentence" effectively eliminated the T-terms as such, while still providing an account of the theory's empirical content.
The evolution of the formula proceeds thus: Step 3 is the complete Ramsey sentence, expressed "RTC," and to be read: "There are some (unspecified) relations such that TC (x1 .
Though Ramsey believed this formulation was adequate to the needs of science, Carnap disagreed, with regard to a comprehensive reconstruction.
In order to delineate a distinction between analytic and synthetic content, Carnap thought the reconstructed sentence would have to satisfy three desired requirements: Requirement 1 is satisfied by RTC in that the existential quantification of the T-terms does not change the logical truth (L-truth) of either statement, and the reconstruction FT has the same O-sentences as the theory itself, hence RTC is observationally equivalent to TC : (i.e., for every O-sentence: O,
This important move satisfies both remaining requirements and effectively creates a distinction between the total formula's analytic and synthetic components.
This is met by using two distinct processes in the formulation: drawing an empirical connection between the statement's factual content and the original theory (observational equivalence), and by requiring the analytic content to be observationally non-informative.
Carnap's reconstruction as it is given here is not intended to be a literal method for formulating scientific propositions.
To capture what Pierre Duhem would call the entire "holistic" universe relating to any specified theory would require long and complicated renderings of RTC → TC.
Instead, it is to be taken as demonstrating logically that there is a way that science could formulate empirical, observational explications of theoretical concepts – and in that context the Ramsey and Carnap construct can be said to provide a formal justificatory distinction between scientific observation and metaphysical inquiry.
Among critics of the Ramsey formalism are John Winnie, who extended the requirements to include an "observationally non-creative" restriction on Carnap's AT – and both W. V. O. Quine and Carl Hempel attacked Carnap's initial assumptions by emphasizing the ambiguity that persists between observable and non-observable terms.