Joseph S. Nye wonders how future historians will judge Trump, looking back at his presidency. Will they think that his waywardness is merely a "temporary aberration or a major turning point in America’s role in the world?" A swallow doesn't necessarily make a sommer. The US has never had a president like him and - hopefully - there won't be any future president like him.

Eight months into his presidendy he is one of the most unpopular presidents in modern history, with an approval rating at 39% after six months in office. Critics say he has achieved the status of a "lame-duck" president, which is usually reserved for the final months of a president's tenure. It's unlikely that he will fare better in the remaining term of his office. "If /he/ avoids a major war, and if he is not re-elected, future scholars may look back at his presidency as a curious blip on the curve of American history. But those are big 'ifs'."

Trump's presidency inspires the author to refer to the 2013 book he wrote on "presidential leadership and the creation of the American era," that aimed to examine foreign policy decisions of eight presidents, and assess the effectiveness and ethics of their choices. Defined as "transformational" or "transactional," the eight presided over the most critical phases of America's rise to world primacy in the twentieth century.

Nye's book asks to what extent did the presidents respond or shape events, and how they reached out to and inspired the public. The most intriguing part is his "What-if" analysis. He speculated on historical alternatives and asked "what might have happened had the president’s most plausible contender been in his place instead. Would structural forces have brought about the same era of US global leadership under different presidents?"

In the past, presidents tried with varying success to forge a new international order while others sought to manage America’s existing position. Trump is no different. He wants to be seen as a transformational leader, one who identifies needed change and creates a vision to guide the change through inspiration, and translates it into action together with like-minded people. But he lacks the managerial skills of a transactional leader, who focuses on supervision, organisation, and performance.

Trump could join the league of transformational presidents like Wilson and Reagan. But instead of changing how America saw the world, Trump changes how the world sees America. In no way can Trump match transactional presidents like Eisenhower and George HW Buch, who were sometimes more effective and ethical. The author's reflections highlight the uneasy relationship between ethical leadership and effective leadership. No doubt Nye's "ethical scorecards" of presidents are controversial, and he doesn't deny the complexity of this judgement, as history is often in the eye of the beholder.

The author's book draws important lessons for today’s uncertain world, in which presidential decision making is more critical than ever. But Trump "with a narcissistic personality and a short attention span, and lacking experience in world affairs, he tends to project slogans rather than strategy in foreign policy." Moreover his tweets do more harm than good. He still hasn't learnt the lesson that sometimes the best presidential decisions are decisions not to act.

The author 's overall assessment is that the most dramatic and inspiring presidents are not always the most effective or ethical. Trump's predecessors, described in the book, had grappled with the changing nature of exercising power in the 21st century effectively and sought to walk a tightrope between managing domestic and international authority, with various degrees of success. "As Robert Frost once put it, when two roads diverge in a wood, taking the one less traveled can sometimes make all the difference." As mercurial as Trump is, the American public still doesn't know where the country is headed. If he is heading for a "do-nothing" presidency, it is still better than plunging the country into a disaster.