Describe the importance of relative chronology to a historian

Relative chronology  is the definition of  events that are placed in chronological order, relative to the time they happened. (you need not know the exact date, though).

a  historian  is  someone who studies the history  based upon a specific period, social phenomenon or a geographical region.

based upon the above definitions, i would think that: it is very crucial for a historian to have  evidence  as to what they think happened. like a lawyer with a trial, you cannot simply state a hypothesis and leave the audience questioning your methods. 

The majority of both parties voted in favor of the bill all senate republicans voted in favor of the bill