Newtonianism

The second field where the contribution of Newtonian philosophy was considered decisive was "experimental philosophy." Newton applied two new principles in this field. Both of them were an outcome of the aforementioned methodological approach he developed in the Opticks and the accompanying "queries."

The first principle was that the only safe way to derive natural laws from the phenomena is to proceed inductively. Hypotheses have no place in this process. Moreover, sticking to this methodological commitment is the only way to protect ourselves from producing natural interpretations built upon "chimerical" suppositions, as was actually the case with Cartesian natural philosophy. "Analysis" (or resolution), as opposed to "Synthesis" (or composition), comprised the core of this method. According to extreme advocates of analytical method, like Abbé Étienne Bonnot de Condillac (1714–1780), analysis was the only correct method of reasoning, because it was taught to humans by nature herself. As a result, even composition would lose its significance: The demonstration of every proposition ought to go over the path of discovery; and the only due method to do so was analysis, not synthesis. It is true that the pronouncement of analytical method has been the source of much confusion, since it has been read by many Newtonians and, evidently, by Newton himself, as if it applies equally to mathematics and to experimental philosophy. On the other hand, however, this same aspect of Newtonian philosophy epitomized the anti-Cartesian stance of many eighteenth-century scholars and became a cornerstone of the natural theology of the time.

The second element Newton introduced to his contemporary experimental philosophy was the quantitative principle. Some fifty years after the first edition of the Opticks, d'Alembert described experiments as processes that aim at intentionally producing new phenomena in order to force nature to disclose her hidden principles. The man who had brought experimental philosophy to its current state was Newton. He had done so by introducing geometry into physics and by unifying experimental practice with mathematical techniques. Thus, he achieved an exact, scrupulous, and innovative science. The object of this science was the study of the general qualities of bodies; observation might help us perceive these properties superficially, but only experiment could bring them forth in a precise and measurable manner. The outcome of this process was the formulation of general quantitative laws, especially for those natural phenomena that were perpetually repeated without making evident their causes or the principles that governed their succession. This same perception, however, was also the limit of Newtonian experimental philosophy: Although Newtonian method was considered the key to unlocking the secrets of nature, from the moment the fundamental laws had become known—as most philosophers believed, in the mid-eighteenth century—the usefulness of experimental physics was rendered limited. Any further investigation of natural effects should come under the field of "mathematical sciences," that is, rational mechanics.