Augustin-Jean Fresnel transformed Young's defense into a powerful physical theory. His work on diffraction and polarization gave mathematical form to wave optics and made it possible to quantitatively predict phenomena the corpuscular theory could not explain. The "Poisson spot" episode — predicted by Fresnel as a consequence of his theory and experimentally verified by Arago — is one of the most dramatic moments in the history of physics: the argument meant to refute the wave theory confirmed it. With Fresnel, wave optics was mathematically consolidated until Maxwell.