secondary source

One reason to read primary source is to get the actual point of view of the people of the time.

For this purpose, secondary source is primary source, for the purposes of figuring out what the people of the time of writing thought about the people of the time written about.  However, this often hinders secondary source in its purpose of revealing the time written about -- 

I'm reading an author who writes that a cunning woman of early modern England had to wait until her husband was in bed before she worked something for healing an illness.  She discusses several possibilities, noting that the law against witchcraft had been repealed in that time, but it does not even seem to have occurred to her as a possibility that he thought it was witchcraft, and therefore wrong.