The historical surroundings of a piece of work are what created it. We must remember that we can not separate ourselves from situated knowledge. Our history or situated knowledge determines what and how we read and interpret. Their history determined how and what they wrote. We come to the reading with our own assumptions.
Authors come to the writings with their own assumptions.
Oh startling development, is that what the new historicism is about, the style and uniqueness. If you could shed some more light on the topic please let me know. As far as I can tell they want the individual to be completely objective. Which by Donna Haraway's essays we can not do. She calls it the God Trick.