Louis Pasteur (1822–1895) French chemist and microbiologist
The life of Pasteur (1911), Volume II http://archive.org/stream/lifeofpasteurtra02valluoft/lifeofpasteurtra02valluoft_djvu.txt. p. 228 <br class="br">Variant translation: "Do not let yourself be tainted with a barren skepticism.", as quoted in The Louisville & Nashville Employes' Magazine Vol. 20 (1944), p. 28