Speaking formally, we might consider a language to contain "redundancy" if there are source programs which produce the same compiled output; if they did it woul

Speaking formally, we might consider a language to contain "redundancy" if there are source programs which produce the same compiled output; if they did it would be "redundant". Since all syntactically erroneous programs produce the same output (presumably none -- obviously I'm excluding e.g. diagnostic error messages here), a language which has more than one syntactically invalid program is redundant. This might not seem all that useful in a practical sense, but I think that's basically the author's point: Such a language would be essentially impossible to write, and thus you're always going to have redundancy. As a result, you should evaluate redundancy in practical terms, rather than viewing it as always needing to be removed.