This is not to sanction Cartesian skepticism, doubting everything in the world and accepting nothing on authority. Some knowledge can only, as a matter of practical reality, come from authority. For example, I believe that the Yankees beat the Mets in the World Series, although I was not there and did not see it happen, because other people who were there tell me the Yankees won. I believe that based upon authority. Even so, authority can be examined.
Some authorities are better, because more accurate and correct, than others.
You listen to your doctor for advice on medicine. You do not listen to your TV repair man for advice on medicine. That is not to criticize those who repair televisions. It is only to point out that they are not doctors. In a democracy, all persons are in theory able to figure out the truth about politicians and politics, such that they can vote and thereby govern themselves.