1434: The Year a Magnificent Chinese Fleet Sailed to Italy and Ignited the Renaissance by Gavin Menzies

Wherein Menzies accuses Renaissance thinkers of Plagiarism, admits the Inadequacy of his Longitude Solution, and claims Zheng He's fleet lies wrecked at the Bottom of Various Oceans. All with the "Controversial New Material" label on the cover of my copy.

This (new) method allows longitude to be determined on any clear day without waiting for a lunar eclipse and without sending messages back to the observer in Beijing. It is a much more advanced method than that described in my book 1421 (that method, kindly explained to me by Professor John Oliver and Marshall Payn, is dependent on eclipses of the moon, which do not happen all that frequently).
-- Chapter 4, How the Star Tables Allowed Longitude to Be Calculated

So... English grammar has a construct called the perfect modal (e.g. "must have", "would have"). We use it to indicate that while we don't have evidence yet for something, we should assume that the evidence exists and see what obtains. Historical analysis should only have these statements when talking about the motivation for the research, or in the closing remarks regarding possible avenues of future research.

Non-Fiction Conjecture:

The Quantity of perfect modals in a text is inversely related to Quality of the text