PG agrees that you can't conclude that beautiful writing, writing that seems plausible and convincing, actually is. Sophistry is writing (or speaking) that seem

PG agrees that you can't conclude that beautiful writing, writing that seems plausible and convincing, actually is. Sophistry is writing (or speaking) that seems plausible and convincing, but is false. PG is not saying that's not possible. What he's saying is that writing that is ugly is highly likely to be wrong. Which has nothing to do with sophistry.