I want to know the answer to the following question:
What idea did Tanselle champion?
All the background I'm provided with is that "This marks a departure from Greg, who had merely suggested that the editor inquire whether a later reading "is one that the author can reasonably be supposed to have substituted for the former", not implying any further inquiry as to why the author had made the change.". Is that enough to answer the question?
Answer: no