Historical materials - things used by historians in their quest to piece together the story of the past.

Theme - a subject or topic.

Change over time - to become different with the passage of time.

Logical inference - a judgment that is believed to be true and that is based on statements, propositions, or judgments that are also believed to be true.

Cause - something that brings about an effect or result.

Effect - something that follows a cause or antecedent.

Historical phenomena - exceptional, unusual, or abnormal persons, things, or occurrences that are of interest to those who investigate the past.

Artifact - an object showing human workmanship or modification.

Credibility - the status of being believable or trusted.

Purpose - an aim or end to be attained.

Perspective - one's mental view of something.

Point of view - a position from which something is considered or evaluated.

Historical questions - questions about the past.

Historical sources - information or evidence that is used to construct an explanation or account of the past.