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|Historical Context=In the 17th century, the “method of hypothesis” (i.e. the hypothetico-deductive method) was popular, but by the 1720s and 1730s it had lost its influence and was replaced by slow, careful inductive methods in the wake of Newton’s ''Principia''.[[CiteRef::Laudan (1981a)|pp. 9-12]] This view was still largely in effect when John Herschel was born in 1792 into a preeminent English scientific family, his father William being a prominent astronomer who is credited with discovering Uranus. He became one of the most respected scientists of his time, and in 1830s England, “one answer to the question of how to be scientific might [have been], ‘Be as much like Herschel as possible.’”[[CiteRef::Cannon (1961a)|p. 219]] He excelled in pure mathematics, optics (he was a pioneer in the technology leading to photography), astronomy and botany (among others). The inductive method of the day remains apparent in influencing Herschel’s work, but he deviates from it in notable ways, resulting in him being part of the movement which revived the method of hypothesis. This movement began in the mid-1700s with scientists like the David Hartley and George LeSage who put forward physical theories on psychology and on the ether, respectively. Their theories were reliant on unobservable entities, and were criticized at the time not for their substance, but for their epistemological basis.[[CiteRef::Laudan (1981a)|p. 119]] Both fought back against this inductivist attack on their work, particularly LeSage, who proposed his own “method of hypothesis” in a series of philosophical essays, in which he contended that Newton’s work was riddled with hypotheses, contrary to the inductivism of the time.[[CiteRef::Laudan (1981a)|pp. 120-122]] Following LeSage, Jean Senebier, a pioneer of photosynthesis research, advocated for the method of hypothesis in his 1775 ''L’Art d’observer'' (later revised in 1802).[[CiteRef::Laudan (1981a)|p. 14]] Dugald Stewart, a prominent Scottish philosopher and mathematician, wrote similarly to LeSage and Senebier, directly influencing Herschel and William Whewell (a friend and colleague of Herschel’s).[[CiteRef::Olson (1975)]] This movement was influenced partly by scientific theories developed in the mid-late 18th century like the wave theory of light, the theory of phlogiston, and Franklin’s fluid theory of electricity, each of which hypothesized unobservables to explain observable phenomena.[[CiteRef::Laudan (1981a)|p. 12]] In other words, these hypotheses decidedly did not come from the aforementioned slow and cautious inductive methods. Given the apparent success of at least the wave theory of light, they had to be pursued, if not necessarily accepted, as scientific theories. And this is where the method of hypothesis, aided by Herschel and his contemporaries/immediate predecessors, came back to become the dominant scientific method.[[CiteRef::Laudan (1981a)|p. 14]]|Major Contributions=In 1831, Herschel published Preliminary Discourse on the Study of Natural Philosophy (PD), his most prominent work in a brief foray into the philosophy of science. Due to his breadth of study, his contribution to this field was mostly limited to his PD, a compact description of his views on the goal of science, theory construction and theory appraisal. Some authors have also compared the methods outlined therein to Herschel’s actual conduct in his scientific endeavors to ascertain his true beliefs on the scientific method , as opposed to the idealized version presented in PD. The sections of PD most relevant to scientific change are parts II and III in which Herschel shares his views on the general concept of a “cause”, on the origin of hypotheses and theories (between which he rarely distinguishes), and on the importance of the deductive appraisal of these theories.

Herschel outlines two methods of science in his Preliminary Discourse - the inductivist method towards the beginning, and the method of hypotheses in later parts. In the beginning he follows the Baconian tradition and advocates for a safe path of induction in which a scientist must reject a method of hypothesis in which a proposed theory is not adequately connected to the phenomena in question.[[CiteRef::Cobb (2012b)|pp. 23-28]] In developing a hypothesis/theory, one must consider the results of the earlier inductive stages of inquiry, and cannot simply use “unrestrained [...] imagination”.[[CiteRef::Herschel (1831)|p. 190]] After a hypothesis is arrived at in an appropriate fashion, one can go on to the important deductive stage of an investigation to “verify the provisional conclusions they have derived”.[[CiteRef::Cobb (2012b)|p. 25]]