The view of probability as an objective degree of belief was developed in the early 20th century by people such as Harold Jeffreys and the the young John Maynard Keynes Keynes1921, and was later adopted by the influential philosopher of science, Rudolf Carnap Carnap1950. This view is not widely held these days, either by statisticians or philosophers, though there seems to be something of recent revival (see for example Williamson 2005 Williamson2005.
