Question

Why does the mechanical philosophy reject Newton’s talk of forces?

Answer 1

Mechanical philosophy was a natural philosophy that became popular in the 17th century. It sought to explain all natural phenomena in terms of matter and motion. Mechanical philosophy proposed that all matter, living or not, was made from the same stuff- tiny particles that joined together in different configurations. The ways in which matter behaved and the ways in which our senses perceived matter were the direct result of the interactions of these irreducible particles. Two of the major developers of mechanical philosophy were Pierre Gassendi and René Descartes. The two men different on a few main points including the indivisibility of matter and the role of God in nature. Gassendi believed that the smallest form of matter was the atom which could not be further divided and existed in a void. Descartes claimed that matter was infinitely divisible and occupied all space. Gassendi thought that God could and did regularly intervene in nature producing phenomena that might not be explained in purely mechanical way.Newton rejected Aristotelianism and endorsed the new mechanical philosophy. However, in his alchemical work, Newton found several natural phenomena that he couldn’t account for in purely mechanical terms. Observing things like differences in solubility, magnetism, and capillary action led him to believe that there were attractive and repulsive forces at play between the particles that made up material bodies. This was problematic because it contradicted the mechanical principle that there is no action-at-a-distance but rather all motion is the result of direct contact with another object. The phenomenon of gravitation illustrated this conundrum quite well.

Newton agreed with Descartes’ natural laws which claimed that matter moved in straight lines and did not deviate from this rectilinear motion unless acted upon by an external force. This made the perpetual, circular orbits of planets very difficult to explain in mechanical terms. Newton resolved the apparent contradiction of gravitational force (and other attractive forces) to mechanical philosophy by appealing to theological explanations. Because the gravitation could not be explained by the material, mechanical world it must be the result of something immaterial, namely God. Like Pierre Gassendi, Newton thought that matter could be endowed with active principles by God at Creation. In his explanation of gravity, Newton demonstrated that a careful examination of natural phenomena necessarily led to God as playing a central role.

Newton was able to mathematize the concept of attractive forces and unify terrestrial and celestial mechanics for the first time in his Law of Universal Gravitation. This work had a profound impact on the field of physics and helped to fuel the Scientific Revolution.