Dialectical describes how someone goes about finding the truth. If you're an investigative journalist, you probably use dialectical reasoning.
You might think dialectical refers to how people speak in a certain region or in a specific group, such as a regional accent. That version of dialect comes from the Greek word dialektos, meaning "discourse, way of speaking." But dialectical instead comes from the French word dialecte, meaning "denoting the art of investigating the truth of opinions." It has to do with a method of reasoning used to determine the truth.