To study nature without fear is possible, but without reproach, impossible.
 Oliver Wendell Holmes Sr., The Poet at the Breakfast-Table (1872). copy citation

Context

“that still another is the result of a congenital tendency which removes the act we sit in judgment upon from the sphere of self-determination, if not entirely, at least to such an extent that the subject of the tendency cannot be judged by any normal standard. To study nature without fear is possible, but without reproach, impossible. The man who worships in the temple of knowledge must carry his arms with him as our Puritan fathers had to do when they gathered in their first rude meeting-houses. It is a fearful thing to meddle with the ark which holds the mysteries of creation.” source