This public lecture was part of the Fourier Analysis @200 workshop at ICMS.

We were delighted to welcome speaker Jean Dhombres (École des hautes études en sciences sociales / The School for Advanced Studies in the Social Sciences, Paris) for this public lecture.

Fourier's life can be read like an adventure novel: the orphan at the age of 10 becomes a Benedictine monk who is freed by the Revolution in 1789, then an actor in the Terror in 1793, professor of Analysis at the Ecole polytechnique at the end of 1795 when he had not yet published anything, responsible for an exploration trip to Upper Egypt before 1800, then prefect of the Empire until 1814. His scientific life is no less contrasted, with a very serious involvement for three years from the end of 1804, when he had already reached the age of thirty-five. Although he ended his career as perpetual secretary of the Academy of Sciences, his Analytic Theory of Heat, already written in manuscript form in 1807, took fifteen years to be published due to various oppositions, including that of the old Lagrange or the young Poisson. And before being recognized by mathematicians who today speak of Fourier analysis as a domain, physicists were the first to make his posterity, then find him again at the origin of the greenhouse effect. It is also a philosopher like Auguste Comte who celebrated Fourier in his Cours de philosophie positive of 1830 as the true positive scientist. However, these different lives have often been too separated by historians. Recent discoveries in museum archives have provided a few portraits made by friends and depicting Fourier at various steps. They will help to let me tell in some short time the story of a man of the Enlightenment, an actor in his time, having connections in extraordinary many circles, and also defender of his work on the eponymous series and integrals.