# Augustin-Jean Fresnel

Augustin-Jean Fresnel (10 May 1788 – 14 July 1827) was a French civil engineer and physicist whose research in optics led to the almost unanimous acceptance of the wave theory of light, excluding any remnant of Newton's corpuscular theory, from the late 1830s until the end of the 19th century. But he is perhaps better known for inventing the catadioptric (reflective/refractive) Fresnel lens and for pioneering the use of "stepped" lenses to extend the visibility of lighthouses, saving unknown numbers of lives at sea.

## Quotes

* Je ne trouve rien de si pénible que d'avoir à mener des hommes.
** I find nothing so painful as having to lead men.
*** Letter to his uncle Léonor Mérimée (29 December 1816), quoted in Œuvres complètes d'Augustin Fresnel (1866), p. xviii]
* Ce n'est point l'observation mais la théorie qui m'a conduit à ce résultat que l'expérience a ensuite confirmé.
** It's not observation but theory that led me to this result that experience has confirmed afterwards.
*** Explaining how he was led to discover the law characterizing interference fringes, in Œuvres complètes d'Augustin Fresnel (1866), p. 61
** Variant translation:
** It was not observation but theory which led me to this result which experience then confirmed.
*** "Google Translate" (2020·05·09)
* Dans le choix d'un système, on ne doit avoir égard qu'à la simplicité des hypothèses; celle des calculs ne peut être d'aucun poids dans la balance des probabilités. La nature ne s'est pas embarrassée des difficultés d'analyse; elle n'a évité que la complication des moyens. Elle paraît s'être proposé de faire beaucoup avec peu : c'est un principe que le perfectionnement des sciences physiques appuie sans cesse de preuves nouvelles.
** In choosing a theory, one should pay attention to simplicity in hypotheses only. Simplicity in computation can be of no weight in the balance of probabilities. Nature is not embarrassed by difficulties of analysis. She avoids complication only in means. Nature seems to have proposed to do much with little: it is a principle that the development of physics constantly supports by new evidence.
*** Œuvres complètes d'Augustin Fresnel (1866), p. 248
** Variant translation:
** In choosing a system, one should only consider the simplicity of the assumptions; that of calculations cannot be of any weight in the balance of probabilities. Nature has not bothered with the difficulties of analysis; it only avoided the complication of means. She seems to have proposed to do much with little: it is a principle that the improvement of the physical sciences constantly supports new evidence.
*** "Google Translate" (2020·05·09)
* Si l'on s'est quelquefois égaré en voulant simplifier les éléments d'une science, c'est qu'on a établi des systèmes avant d'avoir rassemblé un assez grand nombre de faits. Telle hypothèse, très-simple quand on ne considère qu'une classe de phénomènes, nécessite beaucoup d'autres hypothèses lorsqu'on veut sortir du cercle étroit dans lequel on s'était d'abord renfermé. Si la nature s'est proposé de produire le maximum d'effets avec le minimum de causes, c'est dans l'ensemble de ses lois qu'elle a dû résoudre ce grand problème. Il est sans doute bien difficile de découvrir les bases de cette admirable économie, c'est-à-dire les causes les plus simples des phénomènes envisagés sous un point de vue aussi étendu. Mais, si ce principe général de la philosophie des sciences physiques ne conduit pas immédiatement à la connaissance de la vérité, il peut néanmoins diriger les efforts de l'esprit humain, en l'éloignant des systèmes qui rapportent les phénomènes à un trop grand nombre de causes différentes, et en lui faisant adopter de préférence ceux qui, appuyés sur le plus petit nombre d'hypothèses, senties plus féconds en conséquences.
** If one was sometimes led astray by trying to simplify the elements of a science, it is because one has established systems before putting together a fairly large number of facts. Some assumption, which would be very simple when one considers only a class of phenomena, requires many other assumptions if one wants to leave the narrow circle in which we had initially withdrawn. If nature has offered to produce the maximum effect with minimum causes, it is in all of its laws that it had to solve this major problem. It is without doubt difficult to discover the foundations of this wonderful economy, i.e. the simplest causes of phenomena considered from such a wide point of view. But if this general principle of the philosophy of physics does not lead immediately to the knowledge of truth, it can direct the efforts of the human spirit, by leading it away from theories which relate the phenomena to too many different causes, and by adopting preferably those based on the smallest number of assumptions, which show to be more fruitful in consequences.
*** Œuvres complètes d'Augustin Fresnel (1866), p. 249
** Variant translation:
** If we have sometimes gone astray in wanting to simplify the elements of a science, it is because we have established systems before having gathered a large number of facts. Such a hypothesis, very simple when we consider only one class of phenomena, requires many other hypotheses when we want to get out of the narrow circle in which we had first been enclosed. If nature has proposed to produce the maximum of effects with the minimum of causes, it is in all of its laws that it has had to solve this great problem. It is undoubtedly very difficult to discover the bases of this admirable economy, that is to say the simplest causes of the phenomena envisaged under such a wide point of view. But, if this general principle of the philosophy of the physical sciences does not immediately lead to the knowledge of the truth, it can nevertheless direct the efforts of the human mind, by distancing it from the systems which relate the phenomena to too many of different causes, and by making him adopt preferably those who, supported by the smallest number of hypotheses, felt more fruitful as a result.
*** "Google Translate" (2020·05·09)

## External links

* List of English translations of works by Augustin Fresnel.