Roger Bacon, the thirteenth-century scientist, is said to have made important discoveries in optics. He was an early advocate of hands-on experimentation, and as a teacher warned his students against relying uncritically on the opinions of authorities. Nevertheless, this did not stop Bacon himself from appealing to authority when it was expedient for his own argumentation. Thus, Bacon' s work on optics should be generally disregarded, in view of the contradiction between his statements and his own behavior. The reasoning in the argument is flawed because the argument ["criticizes Bacon's character in order to question his scientific findings", "uses Bacon's remarks to his students as evidence of his opinions", 'ignores the fact that thirteenth-century science may not hold up well today', "attacks Bacon's uncritical reliance on authority opinion"]