Charles Bonnet

Charles Bonnet (1720 – 1793) was a Swiss Genevan naturalist and philosopher.

Charles Bonnet in his Recherches sur l’usage des feuilles dans les plantes mentions the different phyllotactic arrangements of leaves, the genetic spiral, and one family of parastichies. He initiated observational phyllotaxis. He studied photosynthesis in plants and noted the emission of bubbles by a submerged illuminated leaf

Pioneering work on experimental entomology (Traité d’insectologie, 1745) incorporates Bonnet’s theory on parthogenesis (development of an egg without sperm observed in female aphids), which would later shape evolutionary opinion.

Bonnet’s description of vivid, complex visual hallucinations in his psychologically normal 87 year old grandfather bears his name – Charles Bonnet syndrome (1760)

  • Born on March 13, 1720 in Geneva, Republic of Geneva
  • 1727 – Partially deaf (aged 7)
  • Received his early education at home from private tutors, becoming interested in entomology during his adolescent years
  • 1740 – Youngest corresponding member of the Académie des sciences in Paris following his work on parthenogenesis
  • 1743 – Doctor of Laws
  • 1743 – Member of the Royal Society of London
  • 1752-1768 Member of the Grand Council of Geneva
  • 1760 – Bonnet suffered progressive visual impairment and by age 40, he was severely visually handicapped. In later life, Bonnet himself experienced visual hallucinations
  • Died on May 20, 1793

Medical Eponyms
Charles Bonnet syndrome (1760)

Condition in which visual hallucinations occur in cognitively intact patients and in the absence of any other psychotic features or any evidence of a psychiatric disorder. Although the syndrome is usually associated with visual impairment, its presence is not essential for diagnosis. CBS can occur at any age, but sufferers are usually elderly.

1760 – Charles Bonnet original description of vivid, complex visual hallucinations in his psychologically normal 87 year old grandfather, Charles Lullin. Lullin had cataract operations on both eyes and was practically blind. His grandfather saw pictures of men, women, birds, carriages, buildings, tapestries and scaffolding patterns.

…je connois un homme respectable, plein de santé, de candeur, de jugement & de mémoire, qui, en pleine veille, & indépendamment de toute impression du dehors, apperçoit de tems en tems, devant lui, des figures d’Hommes, de femmes, d’oiseaux, de voitures, de bâtimens, Il voit voie ces figures se donner différens mouvemens; s’approcher, s’éloigner, suir; diminuer & augmenter de grandeur ; paraître, disparoître, reparaître…

…Il ignore d’un moment à l’autre quelle vision s’offrira à lui: Son Cerveau eft un Théâtre dont les Machine exécutent des Scènes, qui surprennent d’autant plus le Spéctateur qu’il ne les a point prévues.

Charles Bonnet 1760: 426-428

..I know a respectable man, full of health, candor, judgment, and memory, who, in full vigil, and independently of all impression from without, perceives from time to time, before him, figures of men. of women, of birds, of carriages, of buildings. He sees these faces give themselves different motions; to approach, to go away, to follow; decrease & increase in size; to appear, to disappear, to reappear …

…he does not know from one moment to the next what vision will be offered to him: his brain is a theater whose machines perform scenes, which surprise the spectator even more than he could have foreseen.

Charles Bonnet 1760: 426-428


Most often cited as Swiss, however he was a citizen of the independent Republic of Geneva which only joined the Swiss Confederacy on 19 May 1815

Major Publications


BA MA (Oxon) MBChB (Edin) FACEM FFSEM. Emergency physician, Sir Charles Gairdner Hospital.  Passion for rugby; medical history; medical education; and asynchronous learning #FOAMed evangelist. Co-founder and CTO of Life in the Fast lane | Eponyms | Books | Twitter |

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