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From Sunlight to Insight. Jan Ingen Housz, the discovery of photosynthesis & science in the light of ecology

Friday, 29 January, 2010 - 14:30
Campus: Brussels Humanities, Sciences & Engineering campus
Faculty: Arts and Philosophy
Geert Magiels
phd defence

Who discovered photosynthesis?

Not many people know. Jan Ingen Housz’s name has been forgotten, his life and works have
disappeared in the mists of time. The tale of his scientific endeavour shows science in action.
Not only does it open up an undisclosed chapter of the history of science, it also shines some
light on the processes, phenomena and relationships in the development of science.

Dr. Jan Ingen Housz

Jan Ingen Housz (1730 Breda, NL - 1799 Bowood, UK) lived a life of travelling between
Vienna, London, Firenze, Paris and Bath. He was a medical doctor with a broad scientific
interest. He was a close friend of John Pringle, prominent scientist, Royal Physician and
president of the Royal Society. Ingen Housz was appointed as Emperial Physician by Maria
Theresia in Vienna after successfully inoculating her family against smallpox. He befriended
people such as Joseph Priestley and Benjamin Franklin. He kept close contacts with important
scientists of his time, such as Lavoisier, Spallanzani, Van Swieten and Senebier.

The discovery of photosynthesis

Priestley discovered oxygen in 1774, although he didn’t call it as such and probably did not
really understand what he discovered. It would be Lavoisier who would later give this gas its
name and a place in modern chemistry. At that pivotal point in chemical history, where
'oxygen' was coming to replace 'phlogiston', Ingen Housz performed in the summer of 1770
some 500 experiments on plants and wrote down his conclusions in Experiments upon
vegetables, discovering their "great power of purifying the common air in the sun-shine, and
of injuring it in the shade and at night". From this publication and the subsequent articles and
correspondence, it is clear that he was the first to describe and understand the process of
photosynthesis. It is the most important chemical process on earth, as the central reaction that
makes animal life possible, something which Ingen Housz made abundantly clear.

Old story, new perspective.

This underresearched case of scientific enquiry is representative for science as a
method for acquiring trustworthy knowledge. Ingen Housz was a typical exponent of the
Enlightenment, trying to contribute to a better society. His works offer a privileged and
unknown starting point for a philosophical enquiry into the history of biology as well as the
dynamics of science in general, based on as yet unstudied letters and documents and a
reconstruction of his experimental method.

It is also a attempt to an ‘ecological’ approach to the philosophy of science. Science studied
as an ecosystem: individual organisms (scientist are people of flesh and blood), groups of
animals and plants (scientist seem always to operate in groups), their environment (society as
the culture on which scientific knowledge grows and by which it is limited at the same time)
and the flows of energy and information that link all components together and define their
interactions and dynamic equilibrium (the interactions between all these factors in the
multidimensional ‘game’ of science).