 We have seen that the later Carnap relaxed his earlier aspiration to find a unique confirmation function, allowing a continuum of such functions displaying a wide range of inductive cautiousness. Various critics of logical probabilities believe that he did not go far enough — that even his later systems constrain inductive learning beyond what is rationally required. This recalls the classic debate earlier in the 20th century between Keynes, a famous proponent of logical probabilities, and Ramsey, an equally famous opponent. Ramsey (1926; 1990) was skeptical of there being any non-trivial relations of logical probability: he said that he could not discern them himself, and that others disagree about them. This skepticism led him to formulate his enormously influential version of the subjective interpretation of probability, to be discussed shortly.