Actions have consequences. Some things follow inevitably from others. In his third chapter, Amos takes a series of illustrations from the natural world and uses them to demonstrate that when presented with the evidence of one’s eyes and ears, certain conclusions ought to be drawn. He does this by asking seven questions to which every answer is an obvious “No” or “Of course not.”
It may be that the content of the questions is less important than the rhetorical flourish they achieve cumulatively; that each statement is intended to build upon the previous one and together reinforce the certainty of the prophet’s concluding statement. However, when we look at the content of each line more closely in the light of other Old Testament scriptures, it does not seem unreasonable to view them as different ways of illustrating the inevitability of Israel’s coming judgment.