Just In Case Fallacy
The just-in-case fallacy uses an alarming possibility to justify a precaution without adequately assessing its plausibility, consequences, or costs. Planning for a rare catastrophe can still be reasonable.
THE IDEA
Just In Case Fallacy
Also known as: worst case scenario fallacy
Description: Treating the mere possibility of a severe outcome as sufficient reason for a precaution, without adequately weighing plausibility, consequences, and costs. A decision need not focus only on the most probable outcome.
Example #1: It is better to wear a helmet when playing chess because you could fall off your chair and hit your head. The cost of a helmet is small, but the cost of a head injury is huge.
Explanation: Every decision you make has both costs and benefits. Fallacious arguments, like the one above, will attempt to get you to make a decision out of fear rather than reason, thus increasing the perceived cost of choosing not to wear a helmet. Of course, the cost of wearing a helmet while playing chess is peer ridicule of historic proportions.
Example #2: You should worship Jesus just in case he exists, since the cost of worship is small but the cost of not believing is eternal damnation.
Explanation: The attempt is to get you to make a decision out of fear rather than reason, thus increasing the perceived cost of choosing not to worship Jesus for your whole life. The argument also needs to consider incompatible religious claims and the costs of religious practice. Naming an extreme consequence does not establish which claim is true or what choice follows from it.
Exception: When you can come to a reasonable conclusion that preparing for the worst-case scenario is the most economically sound course of action (as in cost/benefit - not necessarily financial), then the fallacy is not committed.
Tip: The example above is a version of Pascal’s Wager. I thoroughly examine (i.e. rip apart) this argument at http://www.relationshipwithreason.com/articles/philosophy/14-pascal-s-wager-the-epitome-of-irrational-rationalism
When to use it
When deciding whether to buy an extended warranty on a cheap product.
When evaluating whether to take a new job offer despite potential downsides.
When making public policy decisions about rare but catastrophic events.
When assessing the risks of a medical treatment with low-probability side effects.
FROM THEORY TO EVERYDAY LIFE
In practice
Wearing a helmet while playing chess
You should wear a helmet while playing chess because you might fall off your chair and hit your head. The cost of a helmet is small, but the cost of a head injury is huge. This argument ignores the probability of falling and the social cost of wearing a helmet.
Worshiping Jesus to avoid Hell
You should worship Jesus just in case he exists, since the cost of worship is small but the cost of not believing is eternal damnation. This argument ignores the probabilities of various religious claims and the cost of worshipping the wrong god.
A MOMENT TO REFLECT
Put it to work.
Think of a recent decision you made fearing the worst possible outcome. How might you evaluate the probabilities instead?
Describe a situation where preparing for the worst-case scenario was actually rational. How does that differ from the Just In Case Fallacy?
Why does the Just In Case Fallacy often lead to irrational decisions? Provide your own example.
CONTINUE THE CONVERSATION
Source texts
- Logically Fallacious - The Ultimate Collection of Over 300 Logical Fallacies