Which is more effective, theory or practice?
1 At another time the problem arose among us whether for the acquisition of virtue practice or theory is more effective, understanding that theory teaches what is right conduct, while practice represents the habit of those accustomed to act in accordance with such theory. To Musonius, practice seemed to be more effective, and speaking in support of his opinion, he asked one of those present the following question: "Suppose that there are two physicians, one able to discourse very brilliantly about the art of medicine but having no experience in taking care of the sick, and the other quite incapable of speaking but experienced in treating his patients according to correct medical theory. Which one," he asked, "would you choose to attend you if you were ill?" He replied that he would choose the doctor who had experience in healing.
2 Musonius then continued, "Well, then, let us take another example of two men. One has sailed a great deal and served as pilot on many boats, the other one has sailed very little and has never acted as pilot. If the one who had never piloted a ship should speak most ably on the methods of navigation, and the other very poorly and ineffectively, which one would you employ as pilot if you were going on a voyage?" The man said he would take the experienced pilot.
3 Again Musonius said, "Take the case of two musicians. One knows the theory of music and discourses on it most convincingly but is unable to sing or play the harp or the lyre; the other is inferior in theory but is proficient in playing the harp and the lyre and in singing as well. To which one would you give a position as musician, or which one would you like to have as teacher for a child who does not know music?" The man answered that he would choose the one who was skilled in practice. 
4 "Well, then," said Musonius, "that being the case, in the matter of temperance and self-control, is it not much better to be self-controlled and temperate in all one's actions than to be able to say what one ought to do?" Here too the young man agreed that it is of less significance and importance to speak well about self-control than to practice self-control. Thereupon Musonius, drawing together what had been said, asked, "How, now, in view of these conclusions, could knowledge of the theory of anything be better than becoming accustomed to act according to the principles of the theory, if we understand that application enables one to act, but theory makes one capable of speaking about it? Theory which teaches how one should act is related to application, and comes first, since it is not possible to do anything really well unless its practical execution be in harmony with theory. In effectiveness, however, practice takes precedence over theory as being more influential in leading men to action."
1 The word έθος which has been translated 'practice' is puzzling. Musonius seems to have in mind some practical school exercise as contrasted with pure theory (λόγος); for conduct in daily life he generally uses πραξις.
2 Unless one bears in mind the background against which they are told, these examples seem altogether too simple and obvious to be worthy of Musonius. Apparently he has developed the thesis that practice is more effective than theory to combat the influence of the older sophists who professed to talk better on any subject than the experts in that field. Cicero (De Oratore II, 75) illustrates the pretentious claims of the sophists by his story of the philosopher Phormio. The presumptuous fellow had the temerity to give a discourse on military strategy, though he had never even seen an army or a camp, before the exiled Hannibal in Ephesus. The rest of the audience was thoroughly delighted, but Hannibal remarked that he had seen a good many crazy people in his life, but never any one crazier than Phormio.