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Emilie du Châtelet on Hypotheses

Kirsten Walsh writes…

Emilie Du Châtelet (1706-1749) is best known in the popular literature as one of Voltaire’s lovers, but among her contemporaries, she was considered to be a brilliant mathematician, physicist and philosopher, whom Voltaire once described as “a great man whose only fault was being a woman”.  Her work on heat and light predicted infrared radiation, and her translation and commentary of Newton’s Principia, published ten years after her death, is still considered to be the standard French translation.  Today I’m interested in Du Châtelet’s views on hypotheses.

Emilie Du Châtelet (1706-1749)

Du Châtelet’s lengthiest discussion of the use of hypotheses in natural philosophy is found in her Institutions de Physique* (1740), which she wrote as a textbook for her thirteen year old son.  Here, Du Châtelet explicitly set up her position on hypotheses in opposition to both Descartes and the Newtonians.  She saw both positions as too extreme; and neither position as correct or useful.  On the one hand:

    “Descartes, who had established much of his philosophy on hypotheses, … gave the whole learned world a taste for hypotheses; and it was not long before one fell into a taste for fictions.  Thus, the books of philosophy, which should have been collections of truths, were filled with fables and reveries.”

But on the other hand, those who follow Newton “have fallen into the opposite excess”:

    “…he alone, who was able to assign and demonstrate the causes of all that we see, would be entitled to banish hypotheses from physics; but, as for us, who do not seem to be cut out for such knowledge, and who can only arrive at the truth by crawling from probability to probability, it is not for us to pronounce so boldly against hypotheses.”

Du Châtelet advocated a more moderate position.  She thought that hypotheses performed several important functions:

Firstly, hypothesising is a good way to get the proverbial ball rolling.  She wrote:

    “There must be a beginning in all researches, and this beginning must almost always be a very imperfect, often unsuccessful attempt.  There are unknown truths just as there are unknown countries to which one can only find the good route after having tried all the others.  Thus, some must run the risk of losing their way in order to mark the good path for others; so it would be doing the sciences great injury, infinitely delaying their progress, to banish hypotheses as some modern philosophers have.”

Secondly, hypotheses can provide useful explanations of the phenomena:

    “When certain things are used to explain what has been observed, and though the truth of what has been supposed is impossible to demonstrate, one is making a hypothesis.  Thus, philosophers frame hypotheses to explain the phenomena, the cause of which cannot be discovered either by experiment or by demonstration.”

So, unlike Newton, Du Châtelet thought that, if we couldn’t obtain certainties, then we should make do with probabilities:

    “The true causes of natural effects and of the phenomena we observe are often so far from the principles on which we can rely and the experiments we can make that one is obliged to be content with probable reasons to explain them.  Thus, probabilities are not to be rejected in the sciences, not only because they are often of great practical use, but also because they clear the path that leads to truth.”

Thirdly, hypotheses suggest new experiments:

    “Hypotheses must then find a place in the sciences, since they promote the discovery of truth and offer new perspectives; for when a hypothesis is once posed, experiments are often done to ascertain if it is a good one, experiments which would never have been thought of without it.”

Moreover, Du Châtelet thought that experimental results could increase the probability of the hypothesis:

    “If it is found that these experiments confirm it, and that it not only explains the phenomenon that one had proposed to explain with it, but also that all the consequences drawn from it agree with observations, its probability grows to such a point that we cannot refuse our assent to it, and that is almost equivalent to a demonstration.”

However, Du Châtelet warned her readers that, when hypothesising, one must proceed with caution:

    “Without a doubt there are rules to follow and pitfalls to avoid in hypotheses.  The first is, that it not be in contradiction with the principle of sufficient reason, nor with any principles that are the foundations of our knowledge.  The second rule is to have certain knowledge of the facts that are within our reach, and to know all the circumstances attendant upon the phenomena we want to explain.”


    “Since hypotheses are only made in order to discover the truth, they must not be passed off as the truth itself, before one is able to give irrefutable proofs.”

So finally:

    “With this precaution one does not run the danger of taking for certain that which is not; and one inspires those who follow us to correct the faults in our hypotheses and to provide what they lack to make them certain.”

Du Châtelet greatly admired the British philosophers, Locke and Newton in particular.  But her views on hypotheses have much more in common with her fellow Continental philosophers, Leibniz and Wolff.


*Translations are quoted from Du Châtelet, E. (2009), Selected Philosophical and Scientific Writings, J. P. Zinsser (ed.), I. Bour & J. P. Zinsser (trans.), University of Chicago Press.

One thought on “Emilie du Châtelet on Hypotheses

  1. Well done.

    Thank you for researching and presenting Du Châtelet’s work. It is close to my own efforts to solve the demarcation problem.
    Happy to correspond with you,