Samuel Johnson (1709-1784), preface to his edition of Shakespeare:
The duty of a collator is indeed dull, yet, like other tedious tasks, is very necessary; but an emendatory critick would ill discharge his duty, without qualities very different from dulness. In perusing a corrupted piece, he must have before him all possibilities of meaning, with all possibilities of expression. Such must be his comprehension of thought, and such his copiousness of language. Out of many readings possible, he must be able to select that which best suits with the state, opinions, and modes of language prevailing in every age, and with his author's particular cast of thought, and turn of expression. Such must be his knowledge, and such his taste. Conjectural criticism demands more than humanity possesses, and he that exercises it with most praise, has very frequent need of indulgence.