"There are two ways in which a science develops; in response to problems which is itself creates, and in response to problems that are forced on it from the outside."

“From any vocabulary of ideas we can build other ideas by formal combinations of signs. But not any set of ideas will be instructive. One must have the right ideas.”

“Until the seventeenth century there was no concept of evidence with which to pose the problem of induction!”

“Opinion is the companion of probability within the medieval epistemology.”

“Much early alchemy seems to have been adventure. You heated and mixed and burnt and pounded and to see what would happen. An adventure might suggest an hypothesis that can subsequently be tested, but adventure is prior to theory.”

“Many modern philosophers claim that probability is relation between an hypothesis and the evidence for it.”

“When land and its tillage are the basis of taxation, one need not care exactly how many people there are.”