Short Answer 
Roosevelt argues for America’s active role in global affairs, asserting that pursuing greatness is crucial, while the counterargument cautions against the potential decline that can accompany aggressive expansionism. This highlights the need for American policymakers to balance ambition with an awareness of historical risks.
Identify the Counterargument
The key counterargument to Roosevelt’s position on America’s “world duties” is presented in the phrase highlighting that nations that have achieved greatness often eventually decline. This serves as a cautionary note against unreserved expansionism and the pursuit of power, suggesting that the pursuit of greatness may come with detrimental consequences.
Understand Roosevelt’s Position
Theodore Roosevelt advocates for America to embrace its role as a global power and to pursue its “world duties” with determination. He believes that the path to greatness is arduous yet essential. This perspective underlines the importance of active participation in global affairs, reflecting patriotism and the nation’s responsibility.
Analyze the Implications
The counterargument warns of the potential risks involved in this pursuit of greatness. It stresses that historical precedents indicate nations that aggressively expand and seek dominance often face decline over time. This analysis prompts a necessary reflection on balancing ambition with caution, urging American policymakers to consider the long-term effects of their actions.