Charles Bonnet

Charles Bonnet (Geneva, 1720 – Genthod, 1793) was a naturalist and philosophical writer from the Republic of Geneva, born into a Protestant family of French origin. He belongs to the European Enlightenment, and his name is tied to the scala naturae, or chain of beings, the view that nature forms a continuous gradation from the simplest creatures to the most perfect. He matters both for his biological observations and for the way he carried them into metaphysics.

He lost his hearing in childhood, which kept him out of school; he was taught privately and trained in law, though his real passion was natural history. Reading Pluche drew him to insects, and his correspondence with Réaumur gave him method. Around 1740 he presented to the Paris Academy of Sciences his experiments on aphids reproducing without fertilisation, known as parthenogenesis, a early contribution that earned him a place as a corresponding member. He also studied respiration in caterpillars and butterflies and the regeneration of freshwater hydra.

As his eyesight failed in mid-century, he turned to theory, writing on psychology, the faculties of the soul and the role of leaves in plants. In 1762 his Considerations on Organised Bodies set out his preformationism: every living being is contained in a pre-existing germ that unfolds, so that all germs were created at the beginning. He used this to oppose epigenesis while staying within the biblical account. His most widely read work, Contemplation of Nature (1764), gave literary form to the chain of beings, and his most ambitious project, the Palingénésie philosophique (1769), extended these ideas to geology, psychology and metaphysics, defending the immortality of the animal soul within a Leibnizian view of the universe.

Bonnet was widely read in his day, though his fixist views and his picture of a nature without leaps were later overtaken by biology. His idea of a parallel between embryonic development and the hierarchy of beings partly anticipates the theory of recapitulation. Voltaire mocked his work, and later thinkers who debated the transformation of species looked back to him.