Common sense is a term whose exact meaning has been debated from Aristotle to Immanuel Kant.

For my purposes, let us define it as the process of using our five senses to perceive, understand and judge events and people. It is doing what most would consider intuitive, obvious and logical. It is a trait important to business, as Lehman learned to their dismay in 2008, and should be in politics.

Unfortunately, it has become rare, at least in the political world. The art of politics involves the ability to persuade and the willingness to compromise. Successful politicians need the judgment and ability to work with and convince opponents to alter policies in a more desirable direction.

Unilaterally, demanding that the ship of state, set on a course of south-south west, should reverse course and head north-north east may be fodder for a campaign speech, but will more likely founder the ship than approach a preferred destination.

The antonym to common sense is irrationality and ineptitude — acting unilaterally, without empathy or regard to consequences. When we abandon common sense, we let in ignorance, we become divisive, we tend to extremes; the result is gridlock.

Politically, it is where we are today. We ignore common goals — goals with which both parties could agree, but that are approached from different directions. For example, we all agree as to the importance of the security and safety of the American people, the elimination of poverty, the need for more rapid economic growth and a stronger middle class.

Persuasion and compromise are the means of achieving common goals. However, when common sense is AWOL, differences become immutable.

Consider two different responses to the tragic shootings last week of nine students at Umpqua Community College in Roseburg, Oregon. Playing to his base, President Obama took the tragedy as an opportunity to rail against the NRA and Republicans.

He was speaking to his choir. There was no mention of mental health. He had no interest in a fair-minded judgment, or solution. His reaction was purely political, intended to divide, not unite.

Jeb Bush sounded callous and insensitive when he said “stuff happens.” But Bush was more honest — not all tragedies can be prevented. Nevertheless, his words were seen as heartless; thus reflective of his character.

We should, though, have a debate over mass killings and gun violence in general, but it should be rational. It should include gun laws, including a discussion as to why strict gun laws have had a minimal effect in places like Chicago and the fact that Umpqua was a gun-free zone.

Questions should be addressed: How do you register guns that are now in the hands of criminals? Why does any civilian need an automatic weapon? What are the objections to a nation-wide registration system?

The discussion must also deal with less politically correct issues, like mental health and the sharing of records. For example, why was Chris Harper-Mercer discharged from the Army after one month of service?

We do not want to violate the Second Amendment, impose ‘Big Brother’ or reinstate the Salem Witch trials, but we should discuss how best to use surveillance and how to share intelligence, including medical and criminal, from myriad sources.

Kevin McCarthy (R-Calif.) showed a lack of sense when he implied that the select committee investigating Benghazi was politically motivated; its real role is to uncover the facts that led to that tragedy. Mr. McCarthy helped Ms. Clinton, hurt his credibility and damaged the investigation.

Peggy Noonan questioned his intelligence. I question his common sense. Speaking of which, the sacking of John Boehner showed little sense on the part of far-right Republicans.

Internationally, we have shown no common sense for years. Citing Vietnam and Iraq, both sides of the aisle argue that the United States cannot and should not “nation-build.” Yet it was in the re-building of Germany, Japan and South Korea where our international policies proved most successful.

Think of the Marshall Plan, which rebuilt a war-torn Europe, especially in places like Greece and Turkey where Soviet Communism was held at bay. That required not just money, but the commitment of troops. Seventy years later we still have 125,000 troops in Germany, Japan and South Korea, or 10 times the numbers we have in Iraq and Afghanistan.

In contrast, it has been in those countries that we abandoned prematurely that have proved most disastrous for those we were trying to help — Vietnam, Iraq and Afghanistan. Today, we have no troops in Vietnam. Supporting the peace, which means keeping troops on the ground in countries where they had been deployed militarily, is less costly than fighting wars and then vacating responsibilities.

After we left southeast Asia in 1975, the Cambodian Communist Pol Pot murdered between 2 and 3 million of his own people over the next four years — proportionately, one of the worst examples of genocide in the history of mankind. The vacuum left by our hasty retreat from Iraq and Afghanistan is being filled sectarianism and killings.

More than 50 times as many Iraqis, Syrians and Afghanis have been killed in the three and a half years since we pulled out as Americans died in the 11 years our troops were on the ground. On the other hand, Europe, Japan and South Korea, where we remained, have seen their people prosper and freedom blossom.

We have seen this abandonment of common sense in financial markets. One would have thought that the lessons of 2008 would be fresh in everyone’s mind, but in persisting in layering on myriad derivative products — many with little real economic value — technologically proficient individuals, using leverage, persist in turning our capital markets — a foundation of free market capitalism — into a casino. They do it because of the prospect for outsized returns for themselves, but with supersized risks for the rest of us.

There will always be disagreements among people. For example, when does life begins, how do we handle the immigration crisis, or what should we do about the estimated 300 million guns in the United States.

But it is extremists (the Tea Party on the right and the Obama-Warren faction on the left) that have allowed the wrecking ball to do its damage. The Clint Eastwood line comes to mind, “If you go far enough to the right you meet the same idiots coming around from the left.”

Ideology and political correctness are the natural enemies of common sense. Campuses that liberally issue trigger warnings create ignorance in the name of well-being, as do student and administrative leaders who disinvite conservative speakers because they find their opinions offensive. Slogans based on lies, like “Hands up! Don’t shoot!” divide, not unite.

If we want growth and prosperity at home, and respect and peace overseas, we need people and institutions with at least a smattering of common sense.