Enlightenment thinkers did not know evolution or thermodynamics.

The claim is about the major Enlightenment thinkers (roughly the late 17th and 18th centuries: e.g. Locke, Hume, Smith, Kant, Voltaire, Spinoza). True: historical evidence shows that the theory of evolution by natural selection (Darwin/Wallace, 1858–59) and thermodynamics as a formal science (the laws formulated c. 1824–1850s by Carnot, Clausius, Kelvin and others) came after these thinkers, so they did not have either theory. Mostly true: this holds in substance, with a minor qualification, e.g. some Enlightenment figures (Buffon, Erasmus Darwin, Diderot, Maupertuis) held speculative transformist ideas, or early heat theory existed, but neither established theory was available. Mixed: one of the two parts holds and the other does not. Mostly false: evidence shows that core Enlightenment thinkers broadly knew a recognisable form of evolution or of thermodynamics, and the claim greatly overstates their ignorance. False: both theories are shown to have been established and known to Enlightenment thinkers.

Set before the research began.

1. E1 Evolutionary Thought Before Darwin Stanford Encyclopedia of Philosophy · 17 June 2019

   “Nonetheless, the period before the middle of the eighteenth century was dominated by a theory of organic generation that effectively precluded the naturalistic development of species.”

2. E2 Evolutionary Thought Before Darwin Stanford Encyclopedia of Philosophy · 17 June 2019

   “In the British Isles in the same period, the reflections in the second volume of his Zoonomia, or the Laws of Organic Life (1794–1796) of Erasmus Darwin (1731–1802), grandfather of Charles Darwin, offered a theory of species development based on a concept of dynamic living matter.”

3. E3 Lesson 2: A History of Thermodynamics and Calorimetry learnthermo.org (thermodynamics course) · 31 March 2026

   “This idea was the right one, and it is an old one: it can be found in Francis Bacon, who wrote as early as 1620 that heat is a form of motion, and also in Descartes.”

4. E4 Lesson 2: A History of Thermodynamics and Calorimetry learnthermo.org (thermodynamics course) · 31 March 2026

   “The general idea of the conservation of energy emerged during the 1840s, partly independently, in the work of Mayer (as early as 1842), Joule, and Helmholtz (1847).”

E4 places the emergence of energy conservation, a core part of thermodynamics, in the 1840s (Mayer, Joule, Helmholtz), after the Enlightenment period. E1 says the dominant theory of organic generation before the mid-eighteenth century effectively ruled out naturalistic species development. There are qualifications: E2 notes that Erasmus Darwin offered a speculative theory of species development in 1794–96, and E3 notes that the idea of heat as motion goes back to Bacon and Descartes. Neither established theory was available to Enlightenment thinkers, so the claim holds in substance with a minor qualification.