Changes

|Historical Context=In the 17th century, the “method of hypothesis” (i.e. the hypothetico-deductive method) was popular, but it “fell into disfavor by the 1720s and 1730s”. It was replaced by the “gradual accumulation of general laws by slow and cautious inductive methods”, influenced by the success of Newton’s Principia. This view remains apparent in influencing Herschel’s work, but he deviates from it in notable ways. Herschel was part of the movement which revived the method of hypothesis, 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 which “hypothesized unobservable entities in order to explain observable processes.” 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 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.

|Major Contributions=John Herschel was born in a preeminent English scientific family, his father William being a prominent astronomer who is credited with discovering Uranus. John 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, ‘Be as much like Herschel as possible.’” He excelled in pure mathematics, optics (he was a pioneer in the technology leading to photography), astronomy and botany (among others). In 1831, he wrote his 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 inductivist method he follows the Baconian tradition and advocates for a “safe and secure path of induction” in which a scientist must reject a method of hypothesis in which a proposed theory is not “properly tethered” to the phenomena in question. In developing a hypothesis/theory, one must consider the results of the earlier inductive stages of inquiry, and cannot simply use “unrestrained [...] imagination”. After a hypothesis is arrived at in an appropriate fashion, one can go on to the important deductive stage of an investigation in order to “verify the provisional conclusions they have derived”.

The third point regards the deductive process of rigorously testing proposed hypotheses, which he regarded as the “essential vehicle of scientific advance”.

Herschel’s views on theory appraisal closely mirror the “deductive” part of the hypothetico-deductive method. When considering a scientific theory, he states that “it is the verification of [the inductions in question] which constitutes theory in its largest sense”. The method of verification is described by means of an example - Herschel describes the process as follows:

1. The construction of the theory: “Inductions drawn from the motions of the several planets about the sun [lead] us to the general conception of an attractive force exerted by every particle of matter in the universe on every other”.