For some, a text is a telegram: composed by a particular person at a particular time, the text’s meaning is clear and doesn’t change. The contemporary reader has direct access to author’s mind in the matter.
To others, a text is a conversation, not only between the author and the reader, but also with all the other readers and hearers in the room, all the editors and redactors who have come before, all the people who carried the text before it was put to paper. The contemporary reader does not have direct access to the author’s mind and wouldn’t want it even if she had it. Those other voices are as much a part of the text’s meaning as the letters initially inked on parchment.
I think the second view is the one that takes a text more seriously.