The two main processes of textual criticism are recension and emendation. Recension is the selection of the most trustworthy evidence on which to base a text. Emendation is the attempt to eliminate the errors which are found even in the best manuscripts. Jerome McGann says these methods innately introduce a subjective factor into textual criticism despite its attempt at objective rules. Alan Cooper discusses this difficulty using the example of Amos 6.12 which reads: "Does one plough with oxen?" The obvious answer is 'yes', but the context of the passage seems to demand a 'no.' Cooper explains that a recombination of the consonants allows it to be read "Does one plough "the sea" with oxen?" The amendment has a basis in the text, which is believed to be corrupted, but is nevertheless a matter of personal judgment.