“You’re sick!” says the diagnostic essay, and students hear the message plainly enough. In classes on connotation, I ask students what the associations of “diagnostic” are. Normally, I don’t need to prod students, but if I do two questions will suffice: “What is a diagnosis?” “Who gives a diagnosis?” A doctor diagnoses a patient with an illness, so a “diagnostic” essay turns students into unhealthy patients and teachers into medical practitioners whose primary job it is to determine what is wrong with the student.