I quote Robert Charles Marsh's introduction to this paper in Logic and Knowledge:
G. E. Moore has pointed out that Russell's `shortest statement' at the close of the paper is faulty because of the ambiguity of the verb `to write'. `Scott is the author of Waverley' does not, therefore, have the same meaning as `Scott wrote Waverley', since Scott (like blind Milton) may be the author of the work without being the person who literally wrote it for the first time. Russell has accepted this correction `with equanimity'. The right to feel patronizing about this slip is reserved by law to those who have done as much for philosophy as Russell and Moore.