"Let us suppose, therefore, that the government is entirely at one with the people, and never thinks of exerting any power of coercion unless in agreement with what it conceives to be their voice." (source: On Liberty: Chapter 2 Of the Liberty of Thought and Discussion By John Stuart Mill)
What does the phrase "Let us suppose" exactly mean here? Does it mean (1) We had better think or believe OR (2) We regard or We literally suppose or imagine?
Which of the two fits the context better? Could you help me clarify it? Thank you always.