How do historians use primary sources to make arguements about the past?

Historians
use primary sources to construct arguments about things that happened. They interpret speeches,
letters, court records, private journals, and a host of other written material to try to
reconstruct events, determine the motives of historical actors, and even to ascertain what
underlying forces affected historical events. Historians analyze these sources for biases,
hopefully not accepting what they have to say at face value. But they use them as evidence to
construct a case in a way that some historians have likened to a courtroom attorney, using them
to try to determine what happened, why it happened, and even how people viewed things that
happened in the past.

The documents and evidence that a historian chooses can
have a serious effect on the types of arguments they make. For instance, historians who studied
the American Revolution by reading the writings of such leaders as Thomas Jefferson or George
Washington might look at the event quite differently than one who studied discipline records of
militia units or local revolutionary committees. It should be noted, in conclusion, that when
they work, historians also engage with the relevant historiography, meaning they read what other
historians have written on the topic they are studying. They build off of (or argue against)
these earlier works by either pointing to new evidence or reading old primary source evidence in
new ways.