The doctrine of spontaneous generation in Aristotle's "Generation of Animals"

c. 340 BCE Life and health theory theory refuted

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The doctrine that small animals arise not from parents but by themselves out of putrefying matter, mud and dew. It is named after this 'spontaneous' generation, spontanea generatio. Aristotle in Book III of Generation of Animals (about 340 BCE), having finished his account of sexual reproduction, separately describes insects, worms and some molluscs as born from non-living matter under the action of heat.

This scheme remained the accepted explanation of the origin of small living things for almost two thousand years and served as the starting point for all later disputes, including Redi's. A late textbook example: Van Helmont's recipe (in the same book as his willow experiment), by which wheat and a dirty shirt produce mice within three weeks. Pasteur dissected it in his Sorbonne lecture of 1864.

Why this date

approximate: the dating of Aristotle's biological treatises is conventional (second half of the 4th century BCE)

Other links

• Redi: meat in sealed and open flasks (Esperienze intorno alla generazione degl'insetti)

  refuted by · Confidence: high

  Redi's experiments with meat in sealed flasks are regarded as a key contribution to the downfall of belief in spontaneous generation, although Redi himself retained it for gall wasps.

  Dispute: The refutation is partial. Parke (2014) shows that Redi did not reject spontaneous generation as such: for galls he accepted it, and this was not a "mistake" but a consistent position within his system. Textbooks present Redi as a complete refutation; historians disagree.

  Link sources

  • Parke 2014, abstract (2014) Verified 20 Sep 2026

    Francesco Redi's seventeenth-century experiments on insect generation are regarded as a key contribution to the downfall of belief in spontaneous generation. Scholars praise Redi for his experiments demonstrating that meat does not generate insects, but condemn him for his claim elsewhere that trees can generate wasps and gallflies.

  • Redi 1668, Parke 2014 (2014) Verified 20 Sep 2026, quotation assembled from fragments

    I placed in four wide-mouthed flasks a snake, some freshwater fish, four eels from the Arno and a piece of milk-fed veal; then, having closed the openings with paper and twine and sealed them well, I put the same materials in four other flasks and left their mouths open: before long the fish and the meat in the latter flasks became maggoty...but in the sealed flasks I never saw a single maggot born.

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong. "Assembled from fragments" means the words do not stand together on the page: we found each fragment separately and joined them with an ellipsis.

• Pasteur: swan-neck flasks and the memoir on organized corpuscles in the atmosphere

  refuted by · Confidence: high

  Pasteur's flask experiments showed that with dust fully excluded a boiled medium stays sterile, and this is regarded as the refutation of spontaneous generation.

  Dispute: Three lines of dispute. (1) Farley and Geison (1974) argued that Pasteur's success was secured by the political and ideological backing of the Academy, and that Pouchet's experiments were no worse; Roll-Hansen (2018) objects: "It was on the conduct of these experiments that the Academy made judgements favorable to Pasteur". (2) Strick (2000) shows that neither the swan-necked flasks nor the dust-free box experiments were regarded as crucial experiments by many authors for a long time, at least into the 1880s (paraphrase; not checked verbatim against the book); in Britain the dispute with Bastian continued until Tyndall's work on heat-resistant spores (1876-1877). (3) Pasteur himself saw the refutation of spontaneous generation as a precondition for germ theory: "He was convinced that his germ theory could not be firmly substantiated as long as belief in spontaneous generation persisted" (Britannica). (4) Pasteur's exemplary case of the doctrine was van Helmont's mice "recipe" (1648), which he dissected in his Sorbonne lecture of 7 April 1864; no verbatim quotation of the lecture has been extracted, and the van Helmont link rests on a paraphrase (Zarka).

  Link sources

  • Britannica, Louis Pasteur: Spontaneous generation (2024) Verified 20 Sep 2026

    These experiments proved that there was no spontaneous generation, since the boiled broth, if never reexposed to air, remained sterile.

  • SEP, Life (2023) Verified 20 Sep 2026

    Two centuries of experiments and debates overturned this view. Louis Pasteur's abiogenesis experiments illustrated that life does not typically come from non-life.

  • Pasteur L. Des générations spontanées; Zarka Y. Pasteur face au dogme de la génération spontanée (Meer) (1864)

    Je vais vous montrer, mesdames et messieurs, par où les souris sont entrées (...)

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

  Further reading

  Not evidence: these carry no quotation and support nothing we wrote. They are books and scans to read next.

  • Farley J., Geison G. L. «Science, Politics and Spontaneous Generation in Nineteenth-Century France: The Pasteur-Pouchet Debate», Bulletin of the History of Medicine 48 (2), 161-198 (1974)
  • Roll-Hansen N. «Revisiting the Pouchet-Pasteur controversy over spontaneous generation: understanding experimental method», History and Philosophy of the Life Sciences 40, 68 (2018)
  • Strick J. E. «Sparks of Life: Darwinism and the Victorian Debates over Spontaneous Generation», Harvard University Press (2000)

Node sources

• Lennox J. «Aristotle's Biology», Stanford Encyclopedia of Philosophy, 5.2 (2023) Verified 20 Sep 2026

  book III, which closes with a discussion of animals that are not sexually generated, including those that arise spontaneously

"Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

Further reading

Not evidence: these carry no quotation and support nothing we wrote. They are books and scans to read next.

• Parke E.C. Flies from meat and wasps from trees: Reevaluating Francesco Redi's spontaneous generation experiments. Stud. Hist. Phil. Biol. Biomed. Sci. 45: 34-42 (2014)
• Van Helmont J.B. (1648) Ortus medicinae (1648)
• Demarest B. Spontaneous Generation in Early Modern Philosophy and Science. Encyclopedia of Early Modern Philosophy and the Sciences (Springer) (2020)

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