The opinions expressed by columnists are their own and do not necessarily represent the views of Townhall.com.

Hillary Clinton has been wrong on one foreign policy issue after another, from the war in Iraq to the war in Libya to the war in Syria. She is secretive, averse to transparency, habitually deceptive and arguably corrupt. She is a risk to lead us into another messy conflict.

Donald Trump has said some things that don't sound bad. He recognizes the invasion of Iraq and the bombing of Libya as mistakes. He vows to refrain from nation building. He says he'd make our allies do more to defend themselves.

So let me be clear: If I had only these two choices of whom to be in charge of U.S. foreign policy for the next four years -- or five minutes -- I would pick Clinton in a heartbeat.

Clinton is a bad option, in the way that Salisbury steak at a roadside diner is a bad option. Trump, however, resembles a tuna sandwich left out on the counter for days: definitely harmful and possibly fatal.

Her speech Thursday, which highlighted the many ignorant, reckless and noxious statements he has made on the subject, should not have been necessary. The president of the United States has more power to do harm than any person on the planet, and such power should be entrusted only to someone who meets a basic standard of knowledge, judgment and maturity. Trump plainly doesn't.

In this realm, as in most areas of government obligations, he combines ignorance and arrogance. He didn't know what the nuclear triad is. He came up empty when asked about Brexit -- Britain's possible exit from the European Union. He insists "we are not a rich country." His chief idea for combating the Islamic State is to "bomb the s--- out of them."

Trump made a big speech on foreign policy in April at an event sponsored by the Center for the National Interest -- which used to be called the Nixon Center, after a president who knew a great deal about the world and how to pursue America's interests in it. Richard Nixon was a terrible president. But had he known less, he would not have been better.

On her worst days, Clinton evokes memories of him -- stiff, charmless, overly enamored of air power, even paranoid. But she also has a wealth of knowledge of the world and many of its leaders, and she needs no on-the-job training in international affairs. At the routine daily business of international diplomacy, Clinton offers competence and predictability.

Trump, however, has Nixon's darkest impulses and none of his understanding. The idea of someone so vindictive, petty and psychologically unbalanced having the power to start World War III ought to induce stark terror in every corner of the globe.

Much of Clinton's Thursday speech consisted of airy banalities -- "We need to be strong at home," for example, and "we need to embrace all the tools of American power." Sometimes she sounded less like a former secretary of state than like Captain Obvious.

But Trump's example makes her platitudes appealing. It's true that he avoids the obvious. No one but him would think to ask, "Who the hell cares if there's a trade war?" No one else would say John McCain, who was tortured during his five years in a North Vietnamese prisoner-of-war camp, was not a war hero. But unconventionality can be a symptom of insanity or stupidity rather than creativity.

Clinton, for all her flaws as a public official and a person, is neither crazy nor clueless. Her establishment credentials and outlook mean her mistakes fall within a predictable range. Knowing something about crafting policy and dealing with foreign leaders might also steer her clear of hazards.

Robert Gates, one of the most informed and sensible people ever to serve as defense secretary, had his differences with her. But in his memoirs, "Duty," he described Clinton as "smart, idealistic but pragmatic, tough-minded, indefatigable, funny, a very valuable colleague, and a superb representative of the United States all over the world."

Trump is doomed to make mistakes because he not only doesn't know much but thinks his lack of knowledge is actually an asset. The less you know, the simpler the world appears. But that's a dangerous illusion.

Giving the presidency to Clinton is far from ideal. But if you needed a major operation, would you choose a surgeon with a haughty manner and a checkered past who loses more than the usual number of patients? Or would you trust the job to a taxidermist?