You discover in your conversations with one physician on common subjects, that he is very slow and cautious in adopting opinions, and when he has once adopted them he adheres to them with great tenacity; while another, on the contrary, is exceedingly changeable in his opinions. These opposite qualities, exhibited as they are abroad in society, go with them to the sick chamber, and they exert their full influence. The one will fix upon a course of practice in a given case with all due consideration, and when he has once fixed upon it, he will pursue it most faithfully, even though the progress of the case may furnish conclusive evidence that he is wrong. He will be blind to that evidence, because he believes most assuredly that he is right in his views of the case. The other will not pursue a course long enough to determine whether it be right, but will see continual reasons for change; and his course from the beginning to the end of a case will often present a medley of variations, from which no intelligent conclusions can be drawn. The one will have a few favorite remedies, which he reckons as old and tried friends, and he adds but few to the little group from year to year. The other will make frequent changes in the remedies which he employs, and will try in rapid succession the new medicines, which every fresh periodical bring to his notice. Some men take strong views of everything which they see. They must always have an opinion, whether the evidence upon which it is based be sufficient or not; and that opinion fills the mind, and actuates all the conduct. They are apt to have very partial and exclusive views, overlooking in their ardor points, which, though they may have little apparent prominence, may, if properly examined, lead to discoveries of great importance. Such men in the medical profession always make a decided impression upon the public mind, and have many strong and ardent friends; and if they possess considerable talent, they generally acquire a dazzling reputation. It is true that they commit frequent and often great errors. But when their bold opinions turn out to be correct, it adds wonderfully to their reputation for acuteness and wisdom, while their errors are mostly concealed, and the whisper that tells of those errors that chance to be discovered, is effectually drowned in the noisy commendation of their enthusiastic adherents. If I at all succeeded in my object in the chapter on the Uncertainty of Medicine, the reader was convinced that there is no pursuit in which a habit of accurate observation is more needed than in the practice of the medical art.