Flaws of Worst-case Thinking

Bruce Schneier writes on the perils of worst-case thinking for CNN.com.

There's a certain blindness that comes from worst-case thinking. An extension of the precautionary principle, it involves imagining the worst possible outcome and then acting as if it were a certainty. It substitutes imagination for thinking, speculation for risk analysis and fear for reason. It fosters powerlessness and vulnerability and magnifies social paralysis. And it makes us more vulnerable to the effects of terrorism.

Schneier goes on to list several logical errors of worst-case thinking:

• There are potential costs and benefits to most situations. By ignoring benefits and acting as if possible costs are certain, accurate risk assessment is compromised.
• It begs the question by assuming that a proponent of an action must prove that the nightmare scenario is impossible.
• It can be used to support any position or its opposite. If we build a nuclear power plant, it could melt down. If we don't build it, we will run short of power and society will collapse into anarchy.
• It validates ignorance. Instead of focusing on what we know, it focuses on what we don't know -- and what we can imagine.

He concludes:

Even worse, it can lead to hasty and dangerous acts. You can't wait for a smoking gun, so you act as if the gun is about to go off. Rather than making us safer, worst-case thinking has the potential to cause dangerous escalation. The new undercurrent in this is that our society no longer has the ability to calculate probabilities. Risk assessment is devalued. Probabilistic thinking is repudiated in favor of "possibilistic thinking": Since we can't know what's likely to go wrong, let's speculate about what can possibly go wrong.

The classic recent example of this in American politics was the disastrous influence of former Vice President Dick Cheney on Bush administration counter-terrorism efforts. Cheney's One Percent Doctrine (from the book of the same name by Ron Suskind) held that threats with even a 1% likelihood must be treated as certainties. This kind of thinking made pre-emptive war and torture of detainees look not just like good ideas but necessities.

--Ballard Burgher