The Pioneer Defended

The Private Science of Louis Pasteur

by Gerald L. Geison
Princeton University Press, 378 pp., $29.95
Louis Pasteur
Louis Pasteur; drawing by David Levine

There is a real world independent of our senses; the laws of nature were not invented by man, but forced upon him by that natural world. They are the expression of a rational world order.”

—Max Planck,
The Philosophy of Physics

Louis Pasteur was the father of modern hygiene, public health, and much of modern medicine. He was born in 1822 at Dole, halfway between Dijon and Besançon in eastern France, where his father owned and ran a small tannery. He attended school in nearby Arbois, obtained his first science degrees in Besançon, and in 1847 graduated with a doctorate in science from the Ecole Normale Supérieure in Paris. Scientists at that time believed that the fermentation of grapes, or the souring of milk, or the putrefaction of meat, were all purely chemical processes unrelated to microorganisms.

The causes of infectious diseases were unknown. Malaria was believed to arise from “miasmas” emanating from swampy ground; outbreaks of plague were attributed to unfavorable constellations, to comets, to the wrath of God, or even to the poisoning of wells by Jews, who often paid for it with their lives. The “animalcules” first observed by the Dutchman Anton van Leeuwenhoek in the seventeenth century were believed to arise spontaneously in decaying meat or vegetable matter; they had not as yet been connected with disease. In the eighteenth century Edward Jenner had introduced vaccination against smallpox with liquid drawn from the pustules of pox-infected cows, but the infectious agents involved were unknown, and vaccination against other diseases did not exist.

Pasteur revolutionized science by proving that fermentation and putrefaction are organic processes invariably linked to the growth of micro-organisms; that these never arise spontaneously from inanimate matter but only by reproduction of their own kind; that they are ubiquitous in the environment, but can be killed by subjecting them to heat, the process now known as pasteurization. He showed that infectious diseases of silkworms, animals, and human beings are caused by microorganisms and he devised ways of preventing them by vaccination. His discoveries inspired Joseph Lister in London to introduce antiseptics into surgery, which reduced mortality to a fraction of what it had been. Shortly before his death in 1895 two of Pasteur’s pupils discovered that bubonic plague is caused by bacteria which are transmitted by fleas from dead rats to man, a discovery that helped to eliminate plague from much of the world.

Pasteur led a simple family life and devoted all his time to research. To generations of Frenchmen and to many others, Pasteur’s has been the image of the selfless seeker after the truth who was intent on applying his science for the benefit of mankind. In The Private Science of Louis Pasteur, Gerald L. Geison, a historian of science, claims to have deconstructed Pasteur, and to have produced “a fuller, deeper and quite different version of the currently…

This is exclusive content for subscribers only – subscribe at this low introductory rate for immediate access!

Online Subscription

Unlock this article, and thousands more from our complete 55+ year archive, by subscribing at the low introductory rate of just $1 an issue – that’s 10 issues online plus six months of full archive access for just $10.

One-Week Access

Purchase a trial Online Edition subscription and receive unlimited access for one week to all the content on

If you already subscribe to the Online or Print + Online Edition, please be sure you are logged in to your account.