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|DOD Approximate=No
|Brief=an English polymath, mathematician, astronomer, chemist, inventor, experimental photographer, and philosopher of science
|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 influenced by in the success 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 be[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 revival movement began in the mid-1700s with scientists like 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 given some consideration pursued, if not necessarily accepted, as good, accurate scientific theories. And this is where the method of hypothesis, aided by Herschel and his contemporaries/immediate predecessors (such as Whewell, LeSage, Senebier, and Stewart), 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.
===== On Causes and the Goal of Science =====
===== On Theory Construction =====
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]]
It is valid, however, to question Herschel’s commitment to this “novice” method (as some authors have labeled it) - he seems to allow for wilder speculation in his method of hypotheses (i.e. his “expert” method), and some have said that the novice method was outlined mainly for rhetorical purposes and that Herschel’s true views were more closely aligned with a more liberal, less restrictive set of guidelines. Bolt claims that Herschel “explicitly encourages and defends the use of hypothetical reasoning” in PD and in related essays, meaning that he did not feel bound to the naive inductivist view outlined above.[[CiteRef::Bolt (1998)]] This was influenced in part by the great success of the wave theory of light, which was a prime example of a theory which could not have come from purely inductive generalizations (whereas Newton’s theory of gravity is an example of one which could have).[[CiteRef::Laudan (1981a)]] In this sense, Herschel contributed to the rise of the hypothetico-deductive method in the 19th-century.
We have next to consider the laws which regulate the action of these our primary agents; and these we can only arrive at in three ways : 1st, By inductive reasoning; that is, by examining all the cases in which we know them to be exercised, inferring, as well as circumstances will permit, its amount or intensity in each particular case, and then piecing together, as it were, these disjecta membra, generalizing from them, and so arriving at the laws desired ; 2dly, By forming at once a bold hypothesis, particularizing the law, and trying the truth of it by following out its consequences and comparing them with facts; or, 3dly, By a process partaking of both these, and combining the advantages of both without their defects, viz. by assuming indeed the laws we would discover, but so generally expressed, that they shall include an unlimited variety of particular laws ; following out the consequences of this assumption, by the application of such general principles as the case admits; comparing them in succession with all the particular cases within our knowledge ; and, lastly, on this comparison, so modifying and restricting the general enunciation of our laws as to make the results agree.[[CiteRef::Herschel (1831)|pp. 198-199]]</blockquote>
The third point regards the deductive process of rigorously testing proposed hypotheses, which he regarded as the “essential vehicle of scientific advance”.[[CiteRef::Cobb (2012a2012b)|p. 32]]
===== On Theory Appraisal =====
In other words, a scientist must assume a proposed law, and test for deviations in an isolated environment. What we can glean from this description is that Herschel thinks a theory is “good” if it has new empirical content, and that if a theory has exceptions in a given domain, it is “positively untrue”, which is consistent with his view on the attainability of ultimate causes.
|Criticism=Herschel’s PD was for the most part well-received by his contemporaries, likely in part due to his high standing in the scientific and philosophical community at the time. It was praised not necessarily for its strength of argumentation (after all, Herschel was not a professional philosopher), but for its practical advice and its portrayal of the ideas of an actual practitioner of science. Darwin even cited it as a personal influence in his autobiography and referenced Herschel in the preface to his ''Origin''. Herschel did face some criticism from William Whewell, who commented that Herschel’s departure from pure inductivism could “foster a spirit of gratuitous theorizing, which will misemploy the cultivators of science, and mislead those who learn it through words alone”.[[CiteRef::Whewell (1831)|p. 400]] However, most views along these lines were silenced in the early 20th century with the acceptance of Einstein’s theory of relativity, which was arrived at partly through Whewell’s feared “gratuitous theorizing”. Overall, criticism was limited due to the scientific environment at the time, in which many speculative theories were experiencing experimental success and gaining acceptance.|Page Status=StubNeeds Editing
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