While US election campaigns are rarely conducive to the making of coherent foreign and national-security policy, the febrile state of America's political environment today seems especially fatal to the endeavour. In circumstances where electoral imperatives privilege point-scoring over policy and rhetoric over rigour, the necessary conditions for thoughtful evaluations of America's place in the world simply do not appear to exist.

By that desultory standard, Donald Trump's latest speech on foreign and national-security policy, delivered in Philadelphia on Wednesday (and his follow-up appearance in a televised forum on national security which also involved Hillary Clinton), lived down to expectations.

In many ways the appearances were in keeping with Trump's previous tone and style. There were routine denunciations of Clinton's recklessness, as demonstrated by her mishandling of sensitive emails, and Obama's fecklessness, which, he argued, had telegraphed American weakness and emboldened China, North Korea and Iran. There were the usual big pronouncements, for example on bolstering US defence spending at no extra cost to the American taxpayer, along with the trademark lack of detail about how such a policy might be achieved. The speech also rested, in at least a few cases, on dubious facts and analysis.

Yet there was an important difference, too. Throughout the speech, Trump appeared to adopt a more 'normal' vision of US foreign policy, marking a departure from some of the radically unorthodox views flagged during his bid for the Republican nomination. The US, he said, would promote 'regional stability' and 'an easing of tensions throughout the world.' It would 'deter, avoid and prevent conflict through unquestioned military strength'. Having apparently banished his earlier ambivalence towards alliances, Trump resolved that the US should 'make new friends, rebuild old alliances, and bring new allies into the fold.' If any of this sounds familiar, it's because these have been the ritual incantations of US foreign policy for much of the past century.

Of course, such a corrective will no doubt be heartening to some. But Trump's gradual conformity has also exposed new tensions and contradictions in his worldview.

His Middle East policy offers a case in point. On the one hand, Trump flagged an end to the kind of overly militarised adventurism he ascribes to Clinton, which he correctly identifies as having produced turmoil, suffering and disorder. Under a Trump Administration, he declared, action in Middle East will be 'tempered by realism.' Gradual reform, not sudden and radical change, would be the overarching objective, and 'diplomacy, not destruction' the approach.

In virtually the next breath, Trump then vowed that one of his first acts as President would be to summon his generals to produce a new plan to 'defeat and destroy ISIS.' This is problematic for at least three reasons. First, and most obviously, it would require precisely the kind of action in the Middle East he claims to reject. As Trump himself acknowledges, it will inevitably involve the deployment of greater resources. Though not militarily unachievable, it will not be easy, and it would entail a significant cost in American lives and treasure.

Second, and more importantly, destroying ISIS would, like the infamous 'surge' in 2007, be unlikely to offer anything more than a temporary abatement of Iraq's problems. ISIS is itself symptomatic of intractable sectarian schisms in Iraqi society. Without a political arrangement in place which either ruthlessly represses Iraq's Sunni population or somehow reintegrates it into the state, destroying ISIS would be like treating a machete wound with a band-aid. For someone vehemently opposed to 'toppling regimes without a plan for the day after', Trump has flagged a willingness to reprise the exact same mistake.

And third, defeating ISIS would hand Iran yet another regional victory, allowing it to consolidate its influence in Iraq . This runs counter to yet another of Trump's policies, articulated in his recent speech, of resurrecting a tighter containment policy that constrains rather than emboldens Tehran.

Beyond the Middle East, there is another contradiction which revealed itself in Trump's speech, and which already bedevils US foreign policy. On the one hand, Trump flagged a commitment to address the problem of allied free-riding, albeit in more tactful language than he's used in the past, 'Early in my term,' he noted, 'I will also be requesting that all NATO nations promptly pay their bills. Additionally, I will be respectfully asking countries such as Germany, Japan, South Korea and Saudi Arabia to pay more for the tremendous security we provide them.' At the same time, however, Trump has flagged an unequivocal commitment to America's global mission, and to the unchallenged military superiority which supports it. If, as Trump claims, his foreign policy would seek to achieve 'peace through strength', why would other states willingly assume greater burdens on behalf of their security?

To this question, like so many others, he is yet to provide an answer.