“Thinking for ourselves is not the same as thinking by ourselves.”
Julian Baggini makes some interesting points. How do you know what to believe, and how do you treat what experts say? I would say, with a healthy dose of skepticism. Any of them could easily be wrong. One answer, I think, is to look at opposing arguments. It also depends on which field you’re looking at, and in the field of morality, the world is the laboratory, so it’s relatively easy to judge the merits of arguments based on how well they explain the world.
We can also look at the quality of someone’s thinking: how daft are the things they say, in general? Can they describe “nuts and bolts”? Are they sober, or hysterical?