Baconian method
The Baconian method is the investigative method developed by Francis Bacon. It is an early forerunner of the Scientific method. The English physician Sir Thomas Browne (1605-82) was one of the earliest scientists to adhere to the scientific empiricism of the Baconian method. His encyclopaedia Pseudodoxia Epidemica (1646-76) includes numerous examples of Baconian investigative methodology; its preface even paraphrases lines from Bacon's essay On Truth from his 1605 work The advancement of learning. The Baconian method was further developed and promoted by J. S. Mill.The method consists of procedures for isolating the cause of a phenomenon, including the method of agreement, method of difference, and method of concomitant variation.
Thus, if an army is successful when commanded by Essex, and not successful when not commanded by Essex: and when it is more or less successful according to the degree of involvement of Essex as its commander, then it is scientifically reasonable to say that being commanded by Essex is causally related to the army's success.
