Argument

New letters from Augustin Fresnel have been uncommon in the literature. This letter was discovered in 2003. It was written to his uncle early in the year 1815 and it gives us a glimpse of Fresnel's state of mind before he emerged on the scientific stage later that same year with a striking essay on light diffraction. In it he tells his uncle of his feelings of agitation at that time. While he believed that he had found something innovative, an explanation of starlight aberration using wave theory instead of corpuscular theory, he felt insecure about how he might deserve the attention of the scientific community, especially given the success of Newton's light theory. The subjects of aether and star aberration were decisive in leading Fresnel to develop his theory.