Overview: Lens on Leeuwenhoek

The ordinary life, extraordinary times, and unprecedented accomplishments of the developer of the single-lens microscope and the first person to see bacteria and protozoa.

Antony van Leeuwenhoek, who lived three hundred years ago in the Netherlands, saw things no one had ever seen before. He made simple, single-lens magnifying glasses that were more powerful than the double-lens microscopes that everyone else was using at the time. His magnifying glasses let him see the tiniest living things: we now call them sperm, red blood cells, protozoa, and bacteria. They were everywhere, but they had no names.

Looking back, we can see their significance. But Leeuwenhoek could not. Everything that he saw, he was the first human ever to see. Before then, in a world as rife with pseudo-scientific speculation as ours, no one even imagined that the microscopic world existed.

The first modern economy

Antony van Leeuwenhoek began making and using his lenses after establishing himself as a cloth merchant and haberdasher in Delft, in the late 1600's, the Golden Age of the Netherlands. The large ships and brave, hardy sailors of the Dutch Republic ruled the world of commerce. The country was called "the most learned state on earth" and produced some of our best paintings, ever.

With their trustworthy financial instruments and international information flow, their cosmopolitan tolerance and long tradition of shared, distributed power, the Dutch used their ingenuity to develop the world's highest standard of living and what some historians call the first modern economy. In 1590, Giovanni Botero wrote,

Holland, without vines, without flax, without wood and with very little cultivated soil, abounds incredibly with wine, linen, ships, and grain.

That economy created a growing, prosperous Delft where Antony van Leeuwenhoek had the liberty to pursue the life of a disinterested, though enthusiastic, and rigorous observer of the little world beyond our sight and, until him, beyond our imagining.

Chatty letters

Leeuwenhoek did not begin to report his observations until he was forty years old. However, he lived, and observed, until he was past ninety. All of his reports, beginning in 1673, were chatty letters to the editors of the journal of England's upstart Royal Society. In 1680, in recognition of his achievements, the Royal Society elected him a Fellow. By his death in 1723, with over a hundred letters published by the journal, he was their most-frequent author, and Delft's most famous citizen, known and celebrated throughout Europe among scientists and those interested in science.

Leeuwenhoek did not know that any of that would happen when, already middle-aged, he began shaping his tiny lenses and mounting them between palm-sized plates and then sticking things on the little pin: plant parts, pond water, and slices of animals' internal organs. He found a cabinet of curiosities and wonders in each specimen.

My aim and striving is to turn the World, as much as it may be possible to me, away from its errors, and to instruct myself.

Mijn doel en streven is de Wereld af te brengen, zoveel als mij mogelijk zal zijn, van zijn dwalingen en mijzelf te onderrichten.

Letter of September 18, 1691 (AB 115) to Antonio Magliabechi

His published letters are personal without being autobiographical. He never wrote about his youth, his years in Amsterdam, his large extended family, his drapery business, his religious practices, or his civic duties. When he mentioned his wife and daughter, he called them (letter of September 12, 1683) "two distinct female persons" (twee distincte Vrouwspersonen). His neighbor was "an old man" (een oud Man).

But we know what he ate and drank and the plants and animals that were part of his everyday life, because he examined them all, in microscopic detail. We know exactly what he spent most of his time doing. He prepared specimens, lenses, and the little metal plates and screws that brought them together. He spent hours looking through them and taking notes. And finally, he wrote the letters, both those collected in Alle de Brieven as well as what must have been the equally voluminous correspondence of daily life that everyone had in the time before telephones and email. Unfortunately, none of his has survived.

"What does it matter?"

He held the microscope as close to his eye as he could, angled into the light, and concentrated. If he told others, perhaps they did not have the patience and curiosity to hold the microscope steady or at the correct angle. Perhaps their eyesight wasn't that good. In any case, they did not always see what Leeuwenhoek saw, tiny moving animals, millions and millions of them, that had no name. He wrote:

Most go to make money out of science, or to get a reputation in the learned world. But in lens-grinding and discovering things hidden from our sight, these count for nought. ... Most men are not curious to know: nay, some even make no bones about saying, What does it matter whether we know this or not?

In the beginning then, Antony van Leeuwenhoek had a problem. He was Adam in a microscopic Garden. What do you do when you see things that no one has ever seen before?