Published online by Cambridge University Press: 28 February 2022
What is the use of probability theory in the sciences? A common answer to this question is: probability is the conceptual tool for statistics, i.e. for the evaluation of collections of numerical data. This reply, that covers a wide range of applications may be rendered by saying that the calculus of probability is the theory for statistical practice. Under this interpretation, probability is part of scientific method; it belongs to the ‘logic’ of science, i.e. it regulates scientific inference. At most, it says something about the state of justified belief of a scientist, but nothing about the nature of his objects.
If I speak of probability as a theoretical concept, I intend to refer to a different use of probability in the sciences; an explanatory use, or - more cautiously put - a use within the framework of explanatory theories, e.g. in microphysics or evolutionary biology. Compared with the standard application to statistics, this use is exceptional and problematical.
Lorraine Daston and Wolfgang Carl have read a first draft of this paper and suggested valuable improvements. I have much benefited from the comment presented by John Norton at the Pittsburgh PSA Conference.