The Kind of Action of the Pluperfect Tense:
Linear and Punctiliar. The past tense of completed action with abiding results.
In this use, verbs that denote a present state in the perfect denote a past state in the pluperfect. These verbs are linear in force, functioning practically like imperfects when put into the past. The reality of the fact is stressed, which present it more strongly than could be done with the aorist. It must be translated into English by the simple past.