The noncanonical gospels are all “unaltered?”  Why does Brown assume that the canonical gospels were subject to so much editing and embellishment while the noncanonical gospels were immune from it?  Where is the evidence that the canonical gospels were “altered” and the noncanonical gospels were “unaltered”?  There just isn’t any.  All ancient texts underwent a process of modification when they were hand copied by scribes; no text was immune from scribal mistakes, omissions, and additions.  Of course this is easy to prove when one has thousands of manuscripts, all of which are somewhat different, and it is difficult to prove when one has only a single (late) copy of a manuscript.  But it is a fact nonetheless.