New evidence, new documents, reinterpretation, failed explanations

These are different forms of historical revision.

New evidence appears

Example:

A newly discovered tax record shows that a supposedly poor medieval region actually had substantial commercial activity.

The previous interpretation may need modification.

New documents are discovered

Example:

A previously unknown political correspondence reveals what ministers discussed privately.

This can change our understanding of their motives.

Old evidence is reinterpreted

The evidence itself does not change.

But historians ask a different question of it.

For example, documents once interpreted as evidence of humanitarian abolitionism may later be examined for their military or economic implications.

Previous explanations fail to explain important facts

Suppose a theory says:

"The revolution happened solely because of economic hardship."

But new evidence shows that economically similar regions did not revolt.

The theory may require revision because it cannot explain the comparative evidence.