Leeuwenhoek’s Character Questioned

Researchers make unwarranted insinuations based on indirect observations of two historic microscopes.

Antony Van Leeuwenhoek is considered the father of microbiology, since he was the first to report the existence of single-celled organisms and bacteria. Our biography of Leeuwenhoek points to his Christian faith, his attention to detail, his rigorous observations and records, and his delight in finding miniature creations of God. Scientists from Rijksmuseum Boerhaave Leiden and TU Delft, in Leeuwenhoek’s home country of the Netherlands, claim he plagiarized the lens-making methods of Robert Hooke but never told Hooke about it. Their claims, however, are based on subjective and insufficient evidence.

New research shows: Antoni van Leeuwenhoek led rivals astray (Delfft University of Technology, via Phys.org). The claims about Van Leeuwenhoek’s reputation start with findings by physicists using neutron tomography to examine two of the microscopes. One of them has a provenance dating to Van Leeuwenhoek’s study; the other can only be traced to 1840. One was said to be high-resolution, the other medium resolution. The physicists could not disassemble the historic devices for fear of damaging them. Neutron tomography allowed them to reconstruct the shape of the lens. They conclude that the 17th-century amateur scientist’s high-powered lens was nothing special:

A microscope used by Antoni van Leeuwenhoek to conduct pioneering research contains a surprisingly ordinary lens, as new research by Rijksmuseum Boerhaave Leiden and TU Delft shows. It is a remarkable finding, because Van Leeuwenhoek (1632-1723) led other scientists to believe that his instruments were exceptional. Consequently, there has been speculation about his method for making lenses for more than three centuries. The results of this study were published in Science Advances on May 14.

The insinuation is that the early microscope-maker boasted without warrant about having special materials and methods. There is no question about his priority in discovering microorganisms, however.

With his microscopes, Antoni van Leeuwenhoek saw a whole new world full of minute life that nobody had previously suspected. He was the first to observe unicellular organisms, which is why he is called the “father of microbiology.” The detail of his observations was unprecedented and was only superseded over a century after his death.

The subsequent criticism, therefore, seems out of place:

His contemporaries were very curious about the lenses with which Van Leeuwenhoek managed to achieve such astounding feats. Van Leeuwenhoek, however, was very secretive about it, suggesting he had found a new way of making lenses. It now proves to have been an empty boast, at least as far as the Utrecht lens is concerned.

Actually, it proves no such thing, as explained below. The article and the paper also claim that Leeuwenhoek used the same lens-making technique that Robert Hooke had used for his book Micrographia, which probably inspired Leeuwenhoek (hence AVL) to begin microscope-making as a hobby. Both men, according to the paper, used flameworking or glassblowing to form small spheres that magnified objects. As the amateur microscopist gained fame for his observations, Hooke apparently sought to find AVL’s secret, but AVL did not reveal it to him. The researchers insinuate that AVL led his rival Hooke astray by not revealing the similarity in lens-making techniques.

We may now assume that Van Leeuwenhoek’s silence was a deliberate choice. The answer to the secret may have been known to Hooke much better than he ever imagined. Van Leeuwenhoek adopted the very lens-making procedure by Hooke soon after he published it, and brought it to a great success, but never told anyone about it.

“Assume” is the operative word. They know from a letter that Hooke was annoyed by Leeuwenhoek’s secrecy, but it is impossible at this time to look into either man’s mind to know their thoughts and motivations. Hooke and the Royal Society valued openness and transparency, but that begs a question: is that a universal scientific obligation? Even today, researchers care very much about priority. Some of them complain bitterly that peer review allows rivals to scoop their discoveries. Even if he preferred secrecy, one cannot fault AVL for whatever measure of distrust he may have had of rivals, especially those in a different country.

Defending Van Leeuwenhoek

Certain facts are undisputed: AVL was the first to observe microorganisms and bacteria. Nobody else improved on his techniques for over a century. Van Leeuwenhoek delighted in giving glory to God. Also, AVL made detailed drawings, shared them with the Royal Society freely, and invited visitors to view objects with his microscopes.

The paper can provide an exercise in avoiding unwarranted assumptions. One of the most obvious is admitted by the researchers: you cannot judge the hundreds of microscopes AVL made from just two examples. Only a handful of AVL’s devices are extant, and we know from his writings he experimented with multiple methods of lens design.

Van Leeuwenhoek’s microscopes enabled the foundation of microbiology, yet due to their maker’s secrecy, the lens-making procedures involved have to be deduced from very scarce sources and references. Of the hundreds of microscopes produced by Van Leeuwenhoek, only a handful has been preserved. Two of these have been submitted to neutron tomography in this research. As a result, a discussion of Van Leeuwenhoek’s lens-making procedures can never be exhaustive; no single procedure can ever be ruled out completely. For instance, a reference in his correspondence informs us that in 1674, Van Leeuwenhoek used the egg of a codfish as a lens, positioned in front of his microscope, to observe a small, reversed image of his surroundings. Exceptional as this experiment may be, it reminds us of the originality and unorthodoxy of Van Leeuwenhoek’s working procedures and warns us that surprises should not be ruled out.

The authors of the paper acknowledge that AVL was a careful and masterful lens-maker and observer. Even if some of his microscopes employed techniques used by others, he took their capabilities farther than others did.

It is notable that Van Leeuwenhoek’s much-heralded 266-powered microscope, unsurpassed in optical performance until the 1830s, turns out to have been produced by a relatively easy and straightforward method, one that was accessible to many. However, notwithstanding his personal skills, Van Leeuwenhoek was definitely well aware of the production methods reported by his contemporaries, and he experimented and implemented their methods as well. Through the successive production of his hundreds of microscopes, Van Leeuwenhoek seems to have fully mastered these grinding and flameworking techniques, to have combined them with appropriate apertures, and to have brought them to perfection, resulting in the superiority of his iconic microscopes in which all the attention and efforts were guided toward their one essential component: the lens.

Those points in mind, consider other points in AVL’s defense:

• One cannot judge a 17th-century scientist by 21st century values and standards.
• AVL was under no moral obligation to tell anyone how he made his devices. His drawings and observations provided the world the essential evidence.
• Anyone else could have used the “production methods reported by his contemporaries” to validate the observations, but nobody apparently did.
• There were other observers who validated the observations at AVL’s home by using the devices.
• Taking Hooke’s method, or the methods of others, and extending and perfecting them beyond what others could do, is hard to distinguish from having a new “secret” method.
• AVL took great care not just with the lens, but with the mount, aperture, polishing and other factors. He figured out how to minimize chromatic aberration and how best to mount and focus the lens.
• Coordinating “to perfection” all the factors required for imagingis much more than a “relatively easy and straightforward method.”

All things considered, Antony Van Leeuwenhoek still deserves his great reputation as the father of microbiology.