“Ask not what disease the person has, but what person the disease has,” the Canadian physician William Osler would often say.

Although he is often described as the father of modern medicine, that particular lesson has not been deeply learned either by medical practitioners or the public at large.

Andreas Lubitz, the 27-year-old German pilot who is believed to have deliberately crashed a Germanwings Airbus A320 airliner in the French Alps, is now reported to have been suffering from depression.

Depression has thus been turned into a one-word explanation for what led to the catastrophic end of Flight 9525.

In the world of simplistic narratives in which we live, a lot of people will now imagine that anyone with depression has the potential to become a mass killer.

But the true story of what led a young man to end his own life and at the same time kill another 149 people, may never be known. It’s quite possible that his deadly impulse did not coalesce into a firm intention until he found himself alone in the cockpit.

William Saletan assumes the dubious role of a fatalistic suicide counselor when writing:

If a person is determined to kill himself, telling him to abstain isn’t enough. The least he can do — and perhaps the most he can do — is to spare the lives of others.

That’s a bit like talking someone down by imploring them not to jump off a building until passersby have cleared the sidewalk. It might sound like a reasonable request, yet it overlooks the tunnel vision of despair. It’s an attempt to appeal to a person’s sense that life is precious when that is the very sense that they have already lost.

In the aftermath of any catastrophic event, we always crave an explanation — a way of understanding what happened, and in this case, a way of becoming confident that something similar will not happen again.

Aircraft crews wear uniforms for a very good reason: we entrust ourselves to their safe care with the expectation that they follow something akin to military discipline in their allegiance to procedure. Uniformity in appearance helps reinforce the expectation of uniformity in behavior. That’s why no airline will ever introduce “casual Friday” where the flight and cabin crews can show up however they please. Even though we know each individual has their own personal life, as passengers we rely on their personal lives not intruding on their work.

Lubitz may have foreseen that his diagnosis was going to destroy his career and concluded that if he couldn’t work as a pilot — if he had to abandon his life’s dream — he had no reason to live. That might explain his suicidal intention, but it wouldn’t explain why he chose to end the lives of everyone around him.

To understand that choice, we might need to understand why he chose to become a pilot in the first place.

Since in piloting the emphasis is on technical proficiency, as passengers we tend not to be too concerned about the pilot’s people skills. Can he land the aircraft safely is all we care — and at least 95% of the time it will be he.

But flying a passenger aircraft doesn’t only require skill in its operation, it also requires a deep sense of responsibility. No doubt most pilots take on and carry that responsibility in an admirable way, but I have to wonder whether in an age of paranoia, the ability and perceived need to isolate the flight crew from the passengers has come at the expense of the human factor.

The flight crew need to be just as concerned about the welfare of the people on board as do the cabin crew and yet within the post 9/11 security constraints it’s common for pilots to get no more than a fleeting glimpse of their own passengers as they pass through the departure gate.

Within the prevailing security mindset, airlines are now being required to consider implementing a rule that many already apply: that whenever a pilot leaves the cockpit another crew member should stand in so that a single pilot is never left alone.

But there might be other procedural changes not directly related to security that could have reduced the risk of the Germanwings tragedy.

Flight crews could just as easily receive passengers and point them to their seats as does the cabin crew. If Andreas Lubitz had met and made eye contact with everyone on the aircraft in this way, he might not have chosen to end their lives — he might even have had second thoughts about ending his own.