Donald Trump’s newly appointed national security adviser, retired Army Lt. Gen. Michael Flynn, doesn’t control the nation’s military, like the secretary of defense. He doesn’t tell America’s diplomats what messages to pass to foreign leaders, like the secretary of state. And he doesn’t tell US spies which governments to infiltrate or which terror leaders to target, like the director of the CIA.

Flynn’s powers are less tangible, but his role is critically important all the same. National security advisers help determine which foreign policy and national security questions reach the president and offer suggestions for how they should be resolved.

That means Flynn will spend more time with President-elect Trump than any other member of the administration’s national security team. He is already helping choose candidates for senior posts while vetoing others, which means Trump’s Cabinet will clearly reflect Flynn’s thinking.

Flynn will have one other responsibility — and this is where the retired general, despite his decades of generally exemplary military service, may be uniquely ill-suited to his role.

From his insistence that President Obama was born abroad to his lies about black-on-white violence, Trump has shown a consistent and troubling habit of absorbing information from semi-factual news sources and treating it as though it were true. That was bad enough when he was just a candidate; it could be disastrous when he’s president.

As Trump begins to slowly roll out picks for key Cabinet posts, it’s unclear whether he will fill his White House with aides willing to present him with information from reputable sources inside and outside of the government that may conflict with his general worldview or beliefs about a specific issue — or whether he will choose staffers who will shape the information flow to reinforce the new president’s existing views about issues like Russia and ISIS.

And that’s why there’s reason to worry about Flynn. A close look at his recently published book, public comments, and tweets reveal a man who swims in the same swamp of hyperpartisan, frequently fabricated, and disturbingly anti-Muslim rhetoric as Trump advisers like Steve Bannon, the white nationalist who was one of the first to receive a West Wing post.

This is apparent from a brief scan of Flynn’s Twitter feed. His tweets include a video that claims “Islam ... wants 80 percent of humanity enslaved or exterminated,” which he captioned “Fear of Muslims is RATIONAL,” and an article from a fake news site claiming that the NYPD was about to arrest Hillary Clinton for “sex crimes with minors,” among other charges.

Flynn is one of those who will most directly determine the new president’s information diet. Based on what he appears to believe, that isn’t reassuring.

How National Security Adviser Flynn could lead Trump astray

Flynn’s official title will be assistant to the president for national security affairs, and in technical terms, his powers and responsibilities are fairly clear.

He staffs and runs the National Security Council, which exists to coordinate and synthesize the sometimes conflicting policy proposals that emerge from the Pentagon, State Department, and other agencies. He communicates the president’s decisions to those agencies and works to ensure they’re implemented. And he presents the president with the strategic assessments of high-level officials like the secretaries of defense and state — and then offers his own thinking.

That would be the case for any national security adviser, and any president. But Flynn is likely to be unusually influential because Trump has never held elected office, served in the military, or dealt with even a fraction of the foreign challenges — from ISIS to a rising China and a revanchist Russia — that he will face. Trump has also made comments on foreign policy that are muddled and sometimes contradictory, like raising questions about America’s security commitments to Japan and South Korea, only to then reassure them that nothing would change. Flynn will need to help the new president decide which path to go down.

“A good national security adviser weighs in on debate to inform it but not sway it,” said Loren DeJonge Schulman, a senior fellow at the Center for a New American Security who formerly served as a top aide to Susan Rice, Obama’s national security adviser. “The truth is that’s incredibly difficult to pull off. Most people who hold that job wind up shading things, even if they’re not trying to.”

In practice, the national security adviser’s powers have been steadily expanding as presidents of both parties concentrate power in the White House. When President Obama was working to normalize ties to Cuba, he entrusted the secret talks to two members of the National Security Council, Deputy National Security Adviser Benjamin Rhodes and then-Latin American director Ricardo Zuniga. Secretary of State John Kerry, according to the Washington Post, wasn’t notified about the negotiations until a late stage. Rice had known about them for months.

One of the most successful recent national security advisers was Stephen Hadley, who held the post under then-President George W. Bush (and is rumored to be in the running for Trump’s defense secretary).

Hadley was a quiet operator whom both the Pentagon and State Department trusted to accurately relay their views to the president before giving Bush his own assessment. Working with his predecessor Condoleezza Rice, then the secretary of state, Hadley successfully marginalized the more hawkish faction in the Bush administration led by Vice President Dick Cheney. He persuaded Bush to agree to the Iraq surge and curtail some of the CIA’s most brutal and controversial detainee interrogation programs.

But if his past record is any guide, Flynn is unlikely to be the type of “honest broker” that has historically made for a successful national security adviser. He was removed from his post running the Defense Intelligence Agency after losing a bureaucratic battle with the CIA and butting heads with his superiors in the Pentagon — one of the government organizations he will now help oversee from his White House post.

Flynn has a serious problem telling true information from false

After retiring in 2014, Flynn has actively sought the limelight, often to express extreme views. During his speech at the Republican National Convention, he led the crowd in chants of, “Lock her up!” demanding Hillary Clinton’s imprisonment.

The tenor of Flynn’s comments has startled other retired officers. Retired Army Gen. Stanley McChrystal, the top commander in Afghanistan when Flynn was running intelligence operations there, reached out to Flynn to urge him to tone down his rhetoric, according to a source familiar with the conversation. Two other retired officers told Vox in separate interviews that they considered Flynn to be “unhinged.”

This might be less of a problem if Flynn were predisposed to push back against some of Trump’s more conspiratorial, racially charged, and anti-Muslim views. The problem is that Flynn seems to share many of them.

He begins his 2016 book, The Field of Fight, by describing his reason for writing it: to expose an anti-American alliance between China, Cuba, and jihadist terrorists that the Obama administration is covering up. This is not an exaggeration; it is literally a defining feature of his worldview:

This administration has forbidden us to describe our enemies properly and clearly: they are Radical Islamists. They are not alone, and are allied with countries and groups who, though not religious fanatics, share their hatred of the West, particularly the United States and Israel. Those allies include North Korea, Russia, China, Cuba, and Venezuela.

There is no evidence that these countries are “allied” with groups like ISIS or al-Qaeda in any meaningful sense of the word. They are not supplying them with weapons, or money, or safe haven. It just makes no sense to speak of an “alliance” between these states and jihadists. Both Russia and China, in fact, are also facing vicious campaigns of Islamist terrorism within their own borders.

Moreover, the idea that countries as diverse as North Korea and Venezuela present some kind of united anti-American foreign policy front is absurd. These countries all have had tense relations with the United States, but in wildly different ways and to varying degrees. They are not part of a united anti-American alliance with each other. Flynn’s construct is like the axis of evil on steroids.

What this speaks to is Flynn’s propensity for hyping up the threat from jihadist groups, and trying to make everything else to fit that frame.

This isn’t someone who’s well-positioned to look at, say, Chinese policy in the South China Sea and give President Trump a reasoned, detail-oriented assessment of Chinese thinking. He’s going to filter that information through his own monomaniacal lens and give Trump a deeply blinkered analysis of what’s going on.

“The rap on him in the intelligence world is that he is great tactically but clueless strategically,” seasoned defense reporter Tom Ricks writes at Foreign Policy. “Not what you want in this slot.”

To make matters worse, Flynn has a serious problem telling true information from false. He seems willing to believe anything that flatters his worldview and casts his opponents in a bad light, no matter how offensive or implausible the information may be. Other tweets alleged a Jewish conspiracy to help Clinton enter the White House (Flynn later deleted his tweet and apologized for it) and falsely accused Clinton of "wearing hijab in solidarity with islamic terrorists."

These aren’t cherry-picked examples. As CNN’s Andrew Kaczynski documents, broadcasting fringe ideas and fake news was pretty par for the course when it comes to Flynn’s Twitter activity.

This was a serious problem when he was chief of DIA. According to the New York Times’s Matthew Rosenberg and Maggie Haberman, he said so many questionable or false things during his time at the agency that his staff coined a term for them: “Flynn facts.”

Remember, now, that analyzing information is the national security adviser’s main job. Flynn’s principal task is going to be taking the information he gets from the military and intelligence agencies and sorting it in a fashion that helps President Trump get a sense of what’s going on in the world and how he should respond to it.

Yet Flynn, clearly, has a lot of difficulty figuring out what information is worthwhile. He seems willing to believe things as absurd as Clinton being involved in a child sex ring, based on a fake news article peppered with transparently silly quotes (one example: “‘What’s in the emails is staggering and as a father, it turned my stomach,’ the NYPD Chief said.”)

Now, instead, imagine Flynn making hard judgment calls about what is and isn’t true. Imagine him in something like the runup to the Iraq War, where choosing to believe the wrong evidence helped push the United States into a disastrous military conflict. And further imagine that the president isn’t George W. Bush, who at least had some knowledge of world affairs and some good advisers, but Donald Trump.

Shortly after Flynn entered the political fray in earnest, he told Foreign Policy’s Sean Naylor that he’s “not going to be a general that just fades away.”

That’s proven true. Whether it’s good for the president he’s been chosen to serve — and the country itself — remains to be seen.