Did All Calorists Believe in Caloric?

There is a lot of literature about how it is that important successes in science apparently stemmed from false belief. Belief in the existence of caloric is a common example: it seems to have led Laplace (1816) to the discovery of the correct speed of sound equation.

However, it seems that many calorists of the time were very cautious about the purported existence of caloric. Here are a few passages worth thinking about.

[i]n our ignorance of the nature of heat, we are left to carefully observe its effects, which principally consist in the dilation of bodies, the rendering of fluids, and the conversion into vapor (Lavoisier and Laplace 1783, 153-154).

Lavoisier and Laplace then go on to suggest a way of translating between caloric and dynamical theories of heat:

  • Free caloric :: Force vive
  • Combining of caloric :: Loss of force vive
  • Disengaging of heat :: Augmentation of force vive

(Lavoisier and Laplace, 154). Lavoisier cautions a few years later:

“we are not even obligated to suppose that caloric is a real substance; it is sufficient… that it be any kind of repulsive cause that separates the molecules of matter, allowing us to imagine its effects in an abstract and mathematical way” (Lavoisier, 1789, 19).

It seems that we must at least tread with great care before inferring what role a particular ontology had in any given scientific discovery.

Laplace. 1816. Sur la vitesse du son dans l’air et dans l’eau. Annales de Chimie et de Physique, 3:328-343.

Lavoisier & Laplace. 1783. Memoire sur la chaleur. Memoires de la Academie des Sciences, 355-408.

Lavoisier. 1789. Traite elementaire de chimie. In Oeuvres de Laplace, premiere tome (1864).

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4 thoughts on “Did All Calorists Believe in Caloric?

  1. Keith Bemer

    You might find it interesting in this regard to examine Carnot’s work on heat engines, in particular his “Reflections of the Motive Power of Heat.”


    Carnot analyzes the operation of heat engines in terms of the movement of caloric from a relatively hotter place to a colder place and the “re-establishment of equilibrium of caloric.” As John Norton discuses in his undergraduate textbook “How Science Works” it seems that Carnot hit upon important insights into thermodynamics using the caloric theory. Soon after, Thomson and Clausius reformulated many of Carnot’s results in terms of the kinetic theory of heat, but it would be interesting to see just how committed Carnot was to the ontology implied by the caloric theory.

    I quickly skimmed the essay and did not find any comments by Carnot regarding the ontological status of the caloric theory. Let me know if you find anything!

  2. Bryan

    Carnot is an interesting case. I think the general consensus among historians is that Carnot was not a calorist — at least in the Reflexions. In particular, Carnot has these posthumously published notes in which he writes:

    “[w]hen a hypothesis is no longer adequate for explaining phenomena, it must be abandoned. This is the case with the hypothesis according to which caloric is considered as matter, as a subtle fluid” (Supplement to Fox’s 1986 edition of the Reflexions.)

  3. Jonathan

    What do you think this comment of Carnot’s has to say about hypotheses that *are* adequate for explaining phenomena? Which phenomena did he have in mind in the case of caloric? And were these phenomena things that he became aware of after working with the idea for a while or was it something he was aware of all along? If the former, did he have an ontological commitment to caloric up until he discovered phenomena for which the caloric hypothesis was not explanatorily adequate? And what was his standard of adequacy? Sorry … way too many questions. Nice post, by the way.

  4. Bryan


    Thanks for all the questions — here’s my shpeel on Carnot. I’m going to number my number my responses and arrange them in the same order.

    1) I’m not aware of any ontological import Carnot explicitly gave to his claims. This makes sense, since Carnot was basically an engineer, and his Reflexions generally targeted an engineering audience.

    2) There are many phenomena covered in Carnot’s treatise, but the exchange of heat and work in heat engines is perhaps the central phenomenon to be described.

    3) I haven’t read any pre-Reflexions manuscripts, and don’t know if any exist. However, the posthumous notes in the Fox edition suggest that Carnot did once believe in caloric, but came to give up the idea. This isn’t surprising, as Carnot was part of an early 19th century French tradition that made central use of the term ‘calorique.’

    4) This term (caloric/calorique) appears throughout Carnot’s Reflexions. However, its appearance is superficial. Carnot makes no interesting commitments about the nature of caloric in his treatise. (Common such commitments of the time would be that caloric is self-repelling, that caloric can couple with ordinary matter, etc. See Laplace’s 1816 article for an example.) Instead, Carnot’s central assumption in his calculation of Carnot-cycle is (roughly) that energy is conserved.

    5) I think it would be fair (at a minimum) to say Carnot wanted ‘adequacy in describing the behavior of heat-engines.’ But of course, the problem for any caloric theory (and a problem that Carnot never solved) was to explain how friction makes real engines fail to be ideal Carnot engines. I think this kind of problem is probably what led Carnot the despairing words I noted above.