Lenses and Waves

248 CHAPTER 6
acquired sufficient reputation – one which would endure forever by his new
discoveries.
But Mr. Descartes, who seems to me to have been very jealous of Galileo’s renown,
[and who] had this great urge to pass for the author of a new philosophy, as appears
from his efforts and his hopes to have it taught at the academies instead of Aristotle’s,
or from his wish that the Society of Jesus embrace it: but in the end because he stuck at
all costs to things once he had put them forward, even though often very wrong ones.”
118
It is not difficult to understand where Huygens placed himself: as the heir of
the unpretentious mathematician rather than the cocky philosopher.
Westman has pointed out he was actually describing himself in his picture of
Galileo as a humble, moderate lover of the truth. 119 With mathematics rather
than philosophy he had made progress in physics.
In Traité de la Lumière he had succeeded to extend it to the causes of
natural phenomena. In it, Huygens took the modest stance he ascribed to
Galileo. His theory was not all-compassing, as he had nothing to say about
colors. 120 After his explanation of strange refraction he described a new
phenomenon (polarization) he had discovered adding that his theory could
not explain it:
“For although until now I have not been able to find its cause, I do not want to refrain
from indicating it, in order to give occasion to others to seek it. It seems that still other
suppositions would have to be made besides the ones I have made; which nevertheless
will not fail to preserve all their probability, after having been confirmed by so many
proofs.” 121
The limited reach of his theory did not alter the fact that only waves could
explain the reflections and refractions of light rays properly.
The focus and the foundation of Traité de la Lumière were on the
mathematical science of optics. In its opening lines Huygens was explicit
about his conception of optics. Optics was one of the sciences where
geometry is applied to matter. He did not explicitly say that he extended this
to the unobservable matter of mechanistic philosophy. He applied geometry
118 OC10, 404. “Galilee avoit du costè de l’esprit, et de la connoissance des Mathematiques tout ce qu’il
faut pour faire des progres dans la Physique, et il faut avouer qu’il a estè le premier à faire de belles
decouvertes touchant la nature du mouvement, quoy qu’il en ait laissè de tres considerables à faire. Il n’a
pas eu tant de hardiesse ni de presomption que de vouloir entrepretendre d’expliquer toutes les causes
naturelles, ni la vanitè de vouloir estre chef de secte. Il estoit modeste et aimoit trop la veritè; il croioit
d’ailleurs avoir acquis assez de reputation et qui devoit durer à jamais par ses nouvelles decouvertes.
Mais M. des Cartes qui me paroit avoir estè fort jaloux de la renommee de Galilee avoit cette grande envie
de passer pour autheur d’une nouvelle philosophie. Ce qui paroit par ses efforts et ses esperances de la
faire enseigner aux academies à la place de celle d’Aristote; de ce qu’il souhaitoit que la societè des Jesuites
l’embrassast: et en fin parce qu’il soutenoit a tort et a travers les choses qu’il avoit une fois avancees,
quoyque souvent tres fausses.”
119 Westman, “Problem”, 97. Yet, in what seems to be a slip of the eye, Westman misses the phrase: “… ni
de presomption que de vouloir entrepretendre d’expliquer toutes les causes naturelles …”
120 Traité, “Preface”.
121 Traité, 88-89. “Car bien que je n’en aie pas pû trouver jusqu’icy la cause, je ne veux pas laisser pour cela
de l’indiquer, afin de donner occasion à d’autres de la chercher. Il semble qu’il faudroit faire encore
d’autres suppositions outre celles que j’ay faites; qui ne laisseront pas pour cela de garder toute leur vraisemblance,
apres avoir esté confirmées par tant de preuves.”