Final answer:
The main idea or problem is the interpretation of primary sources, which is central to the historian's role in understanding the past and identifying causation of historical events.
Step-by-step explanation:
The main idea or problem we have to solve as indicated by the provided information relates to the interpretation of primary sources. In history, these sources are essential as they are firsthand evidence of past events. Historians analyze these sources by considering aspects such as the author, audience, intent, and context to construct a well-founded understanding of historical events. This meticulous process of interpretation facilitates the historian's ability to identify causation in history, unraveling why historical events happened and the factors which shaped our collective past. Interpretation is the key to historical inquiry, commonly leading to historical interpretations that answer foundational questions about our human story. Critical to this process is the corroboration of evidence, comparing and contrasting different sources to develop an accurate portrayal of the past.