Final answer:
Historians question Gavin Menzies' ideas mainly because they lack the concrete evidence needed for historical validation, and his methods have not met the rigorous analytical standards of the discipline.
Step-by-step explanation:
Historians often question the ideas of the writer Gavin Menzies because his theories, particularly those presented in his book '1421: The Year China Discovered the World', require more concrete evidence to be universally accepted. Menzies suggests that the Chinese undertook great voyages that led to the global exploration before the Europeans, which contradicts the more widely accepted historical narratives that prioritize European exploration and discovery. Skepticism toward Menzies stems from a lack of supporting archival and material evidence for his claims, which are seen as necessary to validate his theories. Moreover, the analytical methods of Menzies have been criticized for not adhering to the rigorous standards typically employed by historians. This skepticism is reflective of the historical discipline's broader approach to making interpretations through various lenses, such as Marxism, gender history, and postcolonialism, in what is known as revisionism.