Subsequent to Newton, much has been amended. Thomas Young and Augustin-Jean Fresnel showed that the wave theory Christiaan Huygens described in his Treatise on Light could prove that colour is the visible manifestation of light's wavelength. Science also slowly came to realise the difference between perception of colour and mathematisable optics. The German poet Goethe, with his epic diatribe "Theory of Colours", could not shake the Newtonian foundation - but "one hole Goethe did find in Newton's armour.. Newton had committed himself to the doctrine that refraction without colour was impossible. He therefore thought that the object-glasses of telescopes must for ever remain imperfect, achromatism and refraction being incompatible. This inference was proved by