Converse Error 1
A logical fallacy where the converse of a true conditional statement is assumed to also be true, leading to an invalid inference.
THE IDEA
CONVERSE ERROR 1
If the car is not in our garage, then Jane went downtown.
Jennifer told me she saw Jane downtown.
Therefore, the car won’t be in the garage.
But of course Jane could have gotten downtown by some means other than taking the car, in which case the car probably will be in the garage. Making the error is more likely given some kinds of background knowledge. If Jane rarely goes anywhere without the car, we’re more likely to make the error; if she sometimes takes the bus and sometimes is driven by a friend, we’re less likely to make the error.
When to use it
In legal reasoning, assuming that if a person was at the crime scene, they must be guilty, ignoring alternative explanations.
In medical diagnostics, concluding a disease based on a common symptom without considering other possible causes.
In everyday problem-solving, inferring that a forgotten item must be in the last place you looked because you found it there, without considering that you only looked in that place last.
FROM THEORY TO EVERYDAY LIFE
In practice
Car Garage Example
If the car is not in our garage, then Jane went downtown. Jennifer saw Jane downtown, so it is concluded that the car is not in the garage. However, Jane could have used alternate transportation, making the conclusion invalid.
A MOMENT TO REFLECT
Put it to work.
Can you recall a situation where you assumed that because an outcome occurred, its most common cause must have been present? What other causes could have produced the outcome?
How would you test whether a conditional statement's converse holds in a real-world scenario?
Describe a time when background knowledge influenced your likelihood of committing this fallacy.
CONTINUE THE CONVERSATION
Source texts
- Mindware Tools for Smart Thinking (Richard E. Nisbett)