Constitutionalism means: O a. The powers of government are limited by a set of laws which everyone must follow. These laws are usually written down.
O b. Government power is divided between a central authority and a territorial authority (like a state).
O c. The courts ensure that laws passed are constitutional and go along with what the Constitution says.

the historians cited in the article all agree with one another about the cause of the civil war. despite coming from different backgrounds and cultures, the historians agree that slavery was the root cause of the civil war. the fact that all these historiansgenerally agree with one another makes their shared viewpoints more reliable and valid, especially because the historians have different backgrounds and all work for the well-respected institutions of howard university, clemson university, and the university of colorado.

could you go a bit more in depth with you question? it's quite hard to understand. as soon as you do that i will be glad to : )