Was there energy before 1800? The question surely makes scientists roll their eyes. Energy, after all, was not discovered or invented. It has powered the Sun for billions of years, made organisms grow for millions and driven industrial machines for hundreds. To claim that energy has not always existed must be the product of science illiteracy or vapid posturing by the “other” side in the science wars.

The history of the word “energy” is well charted and uncontroversial. It comes from the Greek energeia, or activity, with the first technical definition of the word being provided by Aristotle. His definition was, however, different from the one that we use today. Every existing thing, he said, has an energeia that maintains it in being and is related to its end or function, or telos. He called a body’s potential or capacity for action its dynamis, and used en-ergeia to refer to the body being “at work” en route to – or at – that telos. As the philosopher Stephen Toulmin has shown, Aristotle’s views derive from the everyday phenomena that he was seeking to explain – in which an agent (such as a horse) faces obstacles (the resistance of road and cart) to keeping a body (the cart) in motion.

Later, however, “energy” lost its technical meaning. In the mid-18th century the Scottish philosopher David Hume complained that the words “power”, “force” and “energy” were virtually synonymous, and “obscure and uncertain”. As late as 1842 the Encyclopaedia Britannica only gave the word the briefest of entries: “ENERGY, a term of Greek origin, signifying the power, virtue, or efficacy of a thing. It is also used figuratively, to denote emphasis of speech.”

The concept

The evolution of the technical concept is likewise uncontroversial. The subjective experience that individuals have of themselves as a centre of action was one factor. Science historian Stanley Jackson has shown, for instance, that Kepler – like many scientists of his age – believed for a time that nature contained soul-like animistic “agents”, treating energy as a secularized version thereof.

“If we substitute for the word ‘soul’ the word ‘force’,” Kepler wrote, “then we get just the principle which underlies my physics of the skies.” Although he now rejected such souls, he concluded that “this force must be something substantial – ‘substantial’ not in the literal sense but…in the same manner as we say that light is something substantial, meaning by this an unsubstantial entity emanating from a substantial body.”

What was Kepler’s “unsubstantial entity”? In the 17th century this question sparked a furious metaphysical and scientific controversy on the existence, nature and measure of force. Descartes spoke of “quantity of motion”, which he defined as mass, m, times velocity, v, whereas Leibniz argued that the force was not just a quantity but a quality of matter, which he called living force or vis viva, given by mv².

The debate continued through the 18th century and was the subject of Immanuel Kant’s first essay. Thomas Young, lecturing to the Royal Institution on collisions in 1807, said that “the term energy may be applied, with great propriety, to the product of the mass or weight of a body, into the square of the number expressing its velocity” – thereby tying the word, apparently for the first time, to its modern concept. But Young’s “energy” was not ours. It referred only to what we now call kinetic energy and did not even use our formulation of ½mv².

Writing on the principle of the conservation of energy, the science historian Thomas Kuhn shows how indebted its formulation was to the phenomena that its creators were trying to explain and to its technological and philosophical context. They were interested in how steam and heat engines operate – particularly the question of how to evaluate and measure their efficiency. They had also recently discovered conversion processes between heat, electricity and other phenomena. Finally, Kuhn pointed out, they were influenced by the philosophical view that sought to explain all phenomena in terms of one or two basic forces.

Addressing a dispute between Joule and Carnot over conceptual and experimental problems involving the interconversion of heat and mechanical work in steam engines, William Thomson (Lord Kelvin) mentioned in 1849 that something involving both work and vis viva was conserved. He did not, however, think that it was yet visible “in the present state of science”. Over the next two decades the full articulation of this insight, involving the recognition that heat was energy – and only one of many forms – would revolutionize science. By the time of the ninth edition of the Britannica in 1899, the entry for “energy” was six pages long and littered with technical terms and equations.

The critical point

So was there energy before 1800?

The common-sense answer is “yes”. Nature does not change, only our ideas about it. Radical “social constructivists”, however, would say “no”, arguing that nature is how we represent it and that the real depends on the consensus of the scientific community. Bruno Latour, for example, argues that things – not just words – have histories. He claims that microbes did not exist before Pasteur discovered them and that Pharaoh Rameses II could not have died of tuberculosis (as now thought) because the bacillus was only discovered in 1882.

These two positions represent different ways of interpreting the above events. Permit me to act annoyingly like a philosopher and say that there is truth in each. The formulation of concepts relies not only on purely theoretical considerations but also on a practical world that is rich in technological devices, such as (in the case of energy) steam engines and temperature-measuring instruments. The network of theoretical considerations and the practical world form a context in which scientific claims can be tested as true or false.

If we emphasize the practical values that permeate this context at the expense of the theoretical considerations, we promote a position similar to that of Latour. If, on the other hand, we emphasize the theoretical considerations rather than the practical and technologically rich horizon, we imply that science represents an ahistorical “reality” apart from a worldly context.

This is the history lesson, in a nutshell, that “energy” has to offer.