Standing on stage at Westminster College, the very place where Winston Churchill delivered his famous 1946 “Iron Curtain” speech and Mikhail Gorbachev declared the end of the Cold War in 1992, Sen. Bernie Sanders offered up his grand vision of US foreign policy.

He spoke of how we can build an idealistic world free of war and famine and terrorism and bloodshed, “a world of peace and economic security for all” in which “people have the decent jobs, food, clean water, education, health care, and housing they need.”

“We must offer people a vision that one day, maybe not in our lifetimes, but one day in the future, human beings on this planet will live in a world where international conflicts will be resolved peacefully, not by mass murder,” Sanders said.

He offered a moving portrait of the world as it should be. What he didn’t offer, though, was any sort of new or innovative or even particularly concrete ideas for how to achieve this grand utopian vision.

Of course, big political speeches like this often present the world as it should be and don’t get bogged down in the details — but especially when it comes to foreign policy, these details really do matter.

Sanders rightly called out America’s many foreign policy sins

Sanders decried the disastrous history of American intervention abroad, reciting a litany of American sins from the 1953 overthrow of the democratically elected leader of Iran to the support for “murderous regimes” in El Salvador, Guatemala, Chile, and elsewhere to the 2003 invasion of Iraq.

He slammed the Obama (and now Trump) administrations for supporting Saudi Arabia’s horrific, brutal war in Yemen, which has killed more than 10,000 civilians since its start in 2015 and triggered one of the most devastating humanitarian catastrophes the world has seen.

Sanders also criticized the “global war on terror,” saying it has been “a disaster for the American people and for American leadership”:

Orienting US national security strategy around terrorism essentially allowed a few thousand violent extremists to dictate policy for the most powerful nation on earth. It responds to terrorists by giving them exactly what they want. In addition to draining our resources and distorting our vision, the war on terror has caused us to undermine our own moral standards regarding torture, indefinite detention, and the use of force around the world, using drone strikes and other airstrikes that often result in high civilian casualties.

He blasted President Trump’s decision to pull the United States out of the Paris climate agreement and warned Trump against withdrawing from the Iran nuclear deal.

“I call on my colleagues in the Congress, and all Americans: We must protect this deal,” Sanders said. “President Trump has signaled his intention to walk away from it, as he did the Paris agreement, regardless of the evidence that it is working. That would be a mistake.”

And he denounced the use of “blustery threats of force” to coerce other countries into changing their behavior and to pursue America’s interests. “[W]hile they might make a few columnists happy,” Sanders said, such threats “can often signal weakness as much as strength, diminishing US deterrence, credibility, and security in the process.”

Taking a stand against things like torture and supporting brutal regimes that wantonly slaughter innocent civilians is laudable, and Sanders should be given due credit for doing so. Criticizing Trump’s decision to pull out of the Paris climate agreement and urging him not to abandon the Iran nuclear deal is sensible policy.

But while condemning American imperialism and Trump’s recklessness might play well with Sanders’s liberal base of support, those things alone do not add up to a comprehensive foreign policy that addresses the myriad international crises and challenges facing the United States today.

Condemning things is good; providing alternative solutions is better

Here’s an example of where Sanders’s foreign policy vision breaks down: He describes terrorism as “a very real threat,” adding:

We will never forget 9/11. We are cognizant of the terrible attacks that have taken place in capitols all over the world. We are more than aware of the brutality of ISIS, al-Qaeda, and similar groups. We also face the threat of these groups obtaining weapons of mass destruction, and preventing that must be a priority.

Yet he decries both full-scale US military intervention and the use of drone strikes and other airstrikes to kill terrorists around the world. That’s all well and good, but then how does he plan to address the threat — both to the US directly and to the security, stability, and prosperity of people around the world — from groups like ISIS and al-Qaeda, if not by some combination of military intervention or drone and airstrikes?

Does he have an alternative idea of how to approach the threat from international terrorist groups, beyond the vague notion that if everyone is happy and prosperous, terrorism will automatically disappear? If he does, he failed to share it with the rest of us during his speech.

Similarly, while Sanders sang the praises of the Iran nuclear deal and encouraged Trump not to pull the US out of it — which would essentially destroy the deal — he never mentions the very real concerns the Trump administration and many of the deal’s supporters and detractors have raised about Iran’s other dangerous and destabilizing actions, such as its support for terrorist groups and sectarian militias throughout the Middle East, its atrocious human rights record at home, and its continued testing of ballistic missiles.

And while he rightly slams the US for supporting Saudi Arabia in its disastrous war in Yemen, he fails to acknowledge that the Obama administration gave that support in the first place in order to convince Saudi Arabia to support the Iran nuclear deal and to do more to help fight ISIS in Syria.

And then there’s North Korea — probably the most acute foreign policy challenge the United States is currently facing and one that carries the threat of potential nuclear war. Sanders correctly acknowledges the failure of past efforts to curb North Korea’s nuclear ambitions and the urgent need to confront the threat.

“Despite past efforts they have repeatedly shown their determination to move forward with these programs in defiance of virtually unanimous international opposition and condemnation,” Sanders said of the North Korean regime.

Yet his prescription for how to solve the problem is just more of the same:

As we saw with the 2015 nuclear agreement with Iran, real US leadership is shown by our ability to develop consensus around shared problems, and mobilize that consensus toward a solution. That is the model we should be pursuing with North Korea. As we did with Iran, if North Korea continues to refuse to negotiate seriously, we should look for ways to tighten international sanctions. This will involve working closely with other countries, particularly China, on whom North Korea relies for some 80 percent of its trade. But we should also continue to make clear that this is a shared problem, not to be solved by any one country alone but by the international community working together.

So we should work together with other countries to tighten sanctions on North Korea and try to get China to cut off its trade ties with the North. In other words, the same basic policy President Trump is currently pursuing and that President Obama pursued before him. How this will magically solve the problem when — as Sanders himself just admitted — it has consistently failed to do so thus far is something Sanders conveniently fails to address.

Sanders also calls for fighting “inequality, corruption, oligarchy, and authoritarianism” globally. “Around the world, we have witnessed the rise of demagogues who once in power use their positions to loot the state of its resources,” he said. “These kleptocrats, like [President Vladimir] Putin in Russia, use divisiveness and abuse as a tool for enriching themselves and those loyal to them.”

He’s absolutely right. But when it comes to exactly how the US should go about fighting these things — especially when the US also needs many of those same corrupt authoritarian governments to work with it on broader challenges like climate change and North Korea — Sanders is noticeably silent.

All this is not to say that Sanders is wrong to criticize the immorality, hypocrisy, and failures of current and past US foreign policy. It’s merely to say that foreign policy is never as simple or as black and white as it seems from the outside.

As Republicans are learning the hard way now with their efforts to repeal and replace Obamacare, it’s one thing to stand on the outside and rail against the policy decisions made by those in power; it’s another thing entirely to come up with actual, workable policies that account for all the messy complexities of the real world.

Idealism and utopian visions of the world may make for great speeches, but they rarely make for coherent foreign policy.