We innovate. Precedent can be valuable or it can be binding. When a problem (from a design problem to a technical detail to a procedural question) seems like an exception to the rule or like a thing that has never been done, recognize the precedents so you can criticize them and foster innovation. Force the consideration of how the present condition fits into common knowledge or is similar to something done before. If this consideration does not spark a solution, it will at a minimum, help illuminate the scope of the problem.