Professionalism: Cases and Ideas in Professional Ethics is a wikibook written mainly by students at the University of Virginia's School of Engineering and Applied Science. The book was begun in the spring semester, 2011; the authors have been students in STS 4600: "The Engineer, Ethics, and Professional Responsibility." This class is the second in a two-semester sequence for fourth-year engineering students. In the fall semesters, students were enrolled in STS 4500: "Case Studies in Technology and Society." This class has produced Lentis, a guidebook to the realm where technological phenomena and social phenomena intersect. As a wikibook, Professionalism will accept contributions from authors and editors all over the world, but the student authors will take particular responsibility to produce a complete, well documented, well written and useful book. Until May 21, 2021, would-be contributors who are not students in the class are asked to consider editing sparingly, but are invited to comment freely on discussion pages, where their suggestions and advice will be welcomed and appreciated. No one's right to edit is in question.