The popular view of a great scientist may have some of its roots in the writing of René Descartes. Descartes believed that science and rhetoric should be kept separate; great science has no need of rhetoric. I hold the opposite view. Scientific ideas are of little use if no one is persuaded of their significance. The greatest scientists are also great rhetors. Louis Pasteur is an excellent example of a scientist whose greatness stems as much from his rhetorical skill as from his experimental methods. Although his science was brilliant, some of the advances most often attributed to him, such as the germ theory of disease, did not actually originate with him at all. He deserves credit for his ability to promote these ideas with powerful rhetorical techniques, but not always for original or groundbreaking work.