It has been the aim of the author in preparing this book to show the application of some of the general principles of logic to the making of a diagnosis. Determining what is the trouble with a patient is essentially a process of reasoning. Many doctors reason well, but others do not, and their patients suffer the consequences. Some "people see, hear and feel all their lives without really learning the nature of things they see. But reason is the mind's eye, and enables us to see why things are, and when and how events may be made to happen and not to happen. We all must reason well or ill, but logic is the science of reasoning and enables us to distinguish between the good reasoning which leads to truth, and the bad reasoning which every day betrays people into error and misfortune." - Jevons.<br><br>In the part on history-taking, an attempt is made to describe some of the difficulties with which the lawyer has had to contend in obtaining the truth from a witness on cross-examination and to show how these same difficulties must be faced by the student or physician in taking a history.<br><br>Some years, ago, the author published a booklet on the "Physical Examination of Surgical Cases."