What is the meaning of this principle: The truth is not known by men, however men are known by way of the truth?
Its meaning is that we do not merely blind follow, as sometimes the blind following is based on an error. Sometimes the jurist is mistaken, the speaker is mistaken. So we do not say "This is the speech of so and so, and it is the truth because so and so is good, or so and so is a scholar, or so and so possesses taqwa. We don't say that as he is not infallible, he does err thus the men are known by the truth.
Those that enact and adopt the evidence they are known to be scholars, and those that have no concern for evidence, they are not the authorities of jurisprudence. They are not the people of knowledge, their speech is not taken such as it is along ever. It's mandatory to subject it to scrutiny of the evidence. So if the evidence bears witness to it, then it's the truth, but if it contradicts the truth it is rejected.
However if he is a jurist that errs, he is rewarded for his independent judgement based on Islamic jurist principles (ijtihaad), but if he is deliberate in his mistake, he sins.