In Libby Prison, during war time, the attempt to prevent written messages being carried out by released prisoners was at first made by the careful examination of the clothing and persons of such prisoners; but this proved to be ineffectual. Then it was decided to put every outgoing prisoner on his word of honor as a soldier in this matter; and that was effectual. A true soldier would require something more than the average treatise on Christian ethics to convince him that a lie to an enemy in war time is justifiable as a "lie of necessity," on the ground of its profitableness. In dealing with the sick, however desirable it may be, in any instance, to conceal from a patient his critical condition, the difference must always be observed between truthful statements that conceal that which the physician, or other speaker, has a right to conceal, and statements that are not strictly true, or that are made for the explicit purpose of deceiving the patient. It is a physician's duty to conceal from a patient his sense of the grave dangers disclosed to his professional eye, and which he is endeavoring to meet successfully. And, in wellnigh every case, it is possible for him to give truthful answers that will conceal from his patient what he ought to conceal; for the best physician does not know the future, and his professional guesses are not to be put forward as if they were assured certitudes. If, indeed, it were generally understood, as many ethical writers are disposed to claim, that physicians are ready to lie as a help to their patients' recovery, physicians, as a class, would thereby be deprived of the power of encouraging their patients by words of sincere and hearty confidence. There are physicians whose most hopeful assurances are of little or no service to their patients, because those physicians are known to be willing to lie to a patient in an emergency; and how can a timid patient be sure that his case does not present such an emergency? Therefore it is that a physician's habit of lying to his patients as a means of cure would cause him to lose the power of aiding by truthful assurances those patients who most needed help of this sort. It is poor policy, as policy, to venture a lie in behalf of a single patient, at the cost of losing the power to make the truth beneficial to a hundred patients whose lives may be dependent on wise words of encouragement. And the policy is still poorer as policy, when it is in the line of an unmistakable sin. And many a good physician like many a good soldier, repudiates the idea of a "lie of necessity" in his profession.