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Electricity: A Speculative Newtonian Experimental Science?

Kirsten Walsh writes…

In his book, Franklin and Newton, I. Bernard Cohen described Franklin’s work on electricity as an example of “Speculative Newtonian Experimental Science”.  The central thesis of our project is that the most common and the most important distinction in early modern philosophy is that between Experimental and Speculative Philosophy.  So ‘speculative experimental science’ sounds like a contradiction in terms.  Today, I’ll consider whether this label is appropriate.

Cohen describes electricity as a Newtonian science that only took off after Newton’s death.  While Newton was fascinated with electrical phenomena, he, like his contemporaries, didn’t really understand it.  However, his discussions of electricity, especially the queries of the Opticks, provided a useful starting point for Franklin’s electrical research.  So we can see why Cohen wants to call Franklin’s electrical research a ‘Newtonian science’.

Newton’s discussions of electrical phenomena are always found in speculative contexts, but they usually have an experimental tone.  For example, Newton first mentioned electrical phenomena in 1675 in his paper on his ‘hypothesis of light’ – which is explicitly a speculative paper.  He specified six hypotheses concerning light and colour.  Hypothesis 1 states that “there is an æthereall Medium much of the same constitution with air, but far rarer, subtiler & more strongly Elastic”.  In the discussion, he suggested that everything is made of æther.  To support this suggestion, he described an experiment involving glass and little pieces of paper.  Using friction, he created static electricity in the glass, and caused the paper to dance around.  He concluded that: “At least the electric effluvia seem to instruct us, that there is something of an æthereall Nature condens’d in bodies.”

Moreover, at various times, Newton speculated that electricity could provide an explanation for gravity.  Again, he discussed this idea in explicitly speculative contexts, and drew on experiments performed by Francis Hauksbee to support his speculations.  For example, in query 31 of the Opticks he asked:

    Have not the small Particles of Bodies certain Powers, Virtues, or Forces, by which they act at a distance, not only upon the Rays of Light for reflecting, refracting, and inflecting them, but also upon one another for producing a great Part of the Phænomena of Nature?

He argued that we have observational and experimental evidence that bodies attract one another by gravity, magnetism and electricity: “and these Instances shew the Tenor and Course of Nature, and make it not improbable but that there may be more attractive Powers than these.”

Despite all this speculating, Newton displayed epistemic caution:

    For we must learn from the Phænomena of Nature what Bodies attract one another, and what are the Laws and Properties of the Attraction, before we enquire the Cause by which the Attraction is perform’d.  The Attractions of Gravity, Magnetism, and Electricity, reach to very sensible distances, and so have been observed by vulgar Eyes, and there may be others which reach to so small distances as hitherto escape Observation; and perhaps electrical Attraction may reach to such small distances, even without being excited by Friction.

The final paragraph of the General Scholium of the Principia echoes these ideas:

    A few things could now be added concerning a certain very subtle spirit pervading gross bodies and lying hidden in them; by its force and actions, the particles of bodies attract one another at very small distances and cohere when they become contiguous; and electrical bodies act at greater distances, repelling as well as attracting neighbouring corpuscles… [However,] there is not a sufficient number of experiments to determine and demonstrate accurately the laws governing the actions of this spirit.

From these passages, it’s easy to see why Cohen calls Newton’s electicity ‘speculative experimental science’: Newton’s discussions of electricity are speculative in tone, and yet they can be considered experimental, since they draw on experimental and observational evidence.  However, there is a sense in which this label isn’t appropriate.  I have previously argued that this kind of speculation has a role within Newton’s experimental philosophy.  The epistemic caution displayed by Newton suggests that he is indeed following his methodology and that these discussions of electrical phenomena are taking place within his experimental philosophy.  So Newton’s electrical work shouldn’t be taken as an example of ‘speculative philosophy’.  Taken in this sense, the label ‘speculative experimental’ is indeed an oxymoron.