People often admonish us to learn the lessons of history, but, even if it were easy to discover what the past was really like, it is nearly impossible to discover its lessons.
Conclusion (implicit)
It's kind of absurd to urge people to learn the lessons of history.
Evidence
It's nearly impossible to discover the lessons of history (for example, what were lessons of WWI?) And even if you learned the lessons, how would you know when to apply them, since no future situation will exactly match a past situation.
Evaluate
This is a weird Role question. They're asking us about a claim that never happened. The paragraph never said "we should learn the lessons of history". But people often admonish us to learn the lessons of history.
That's saying that people often say, "We should learn the lessons of history".
So the question stem is asking, what Role is played by [the idea that people often say].
Goal
Since this whole argument is rebutting that first notion, that we should learn the lessons of history, we could say the Role played is a counterpoint an opposing conclusion the claim the argument is trying to undermine the enemy