1. Formal logic is concerned with nothing but the rules of consistent thought. In addition to this we have certain 'useful mental habits' for handling the material with which we are supplied by our perceptions and by our memory and perhaps in other ways, and so arriving at or toward truth; and the analysis of such habits is also a sort of logic;it,1931
2. Keynes then immediately goes on to propose a mild skepticism about an aspect of Ramsey's notion of probability: But in attempting to distinguish 'rational' degrees of belief from belief in general he [Ramsey] was not yet, I think quite successful. It is not getting to the bottom of the principle of induction merely to say that it is a useful mental habit. Yet in attempting to Archival sources ASP/FPR;01 Frank Plumpton Ramsey Papers, Archives of Scientific Philosophy,1983