Evan Solomon, host of CBC Radio's The House, reflects on why words matter in times of crisis in his weekly radio essay as heard on April 27, 2013.

Prime Minister Stephen Harper took another not–so–veiled swipe at Liberal leader Justin Trudeau when he said "this is not a time to commit sociology, if I can use an expression."

Harper was referring to part of the answer Trudeau gave in an interview with Peter Mansbridge just hours after the Boston bombings, when he said "Over the coming days we have to look at the root cause. Now we don't know now whether it was terrorism or a single crazy or a domestic issue or a foreign issue… But there is no question that this happened because there is someone who feels completely excluded, completely at war with innocents, at war with a society."

Harper first said Trudeau was "rationalizing" and now he said Trudeau is committing "sociology." And this has now kicked off a two week long debate about the appropriate response to a terrorist attack.

A debate that became much more poignant this week in when two men were arrested here in Canada on charges that they were attempting to bomb a Via train.

This, only weeks after news emerged that two young Canadians from London, Ont., went to Algeria to take part in a horrific terrorist attack there.

Terrorist attacks, bombings, shootings, all require a very specific kind of leadership, certain words.

But who decides what words are appropriate? If Trudeau's initial response to the bombing doesn' t pass the smell test to voters, he'll have to be accountable. That's the job he has.

But what exactly did the prime minister mean when he said "this is not a time to commit sociology"?

I asked Conservative MP Pierre Poilievre what the prime minister meant.

"Root causes of terrorism, is terrorists," Poilievre said on CBC's Power and Politics.

As simple as that. The root cause of terrorism is terrorists.

Now does that mean that the search to find out why people turn to violence, why young people radicalize, why some shoot up movie theatres or schools — that it's all somehow rationalizing what they do if we ask why?

U.S. President Barack Obama condemned the violence immediately after the Boston bombings saying, "we still do not know who did this or why and people shouldn't jump to conclusions before we have all the facts. But make no mistake, we will get to the bottom of this. And we will find out who did this, we'll find out why they did this."

Obama condemned the violence, but he seems to also be asking why? Why it happened. And it's not much different in Britain, under conservative Prime Minister David Cameron.

In 2010, Cameron presented his government's Strategic Defence and Security Review. It was called 'Securing Britain in an Age of Uncertainty.'

In it, Cameron wrote "we must find more effective ways to tackle risks to our national security" and "treat the causes, rather than having to deal with the consequences."

The report goes on to say the second most important national security taks is "to tackle at root the causes of instability."

That's their security mandate in the U.K. — to ask "why?"

Is Cameron committing "sociology", to use the phrase of the week?

In a crisis words matter, especially for leaders dealing with the security of citizens in the face of of terror.

But it's interesting to see, in this crisis in Canada, that one word has become radioactive.

Why?