The Post Hoc Ergo Propter Hoc fallacy, commonly referred to as “Post Hoc”, is a logical error where one assumes that if event A occurs before event B, then event A must have caused event B. The phrase “Post Hoc Ergo Propter Hoc” is Latin for “after this, therefore because of this”.
Definition and Example
The fallacy occurs in reasoning when a subsequent action is assumed to be the consequence of a preceding event without any logical connection between the two. For example, attributing a falling birth rate to a previous reduction in a stork population is a classic illustration of this fallacy. The two events are coincidental, not causally related.
Historical Context
The term “Post Hoc Ergo Propter Hoc” derives from medieval scholasticism and has been recognized as a fallacy in logical arguments since ancient times. It often surfaces in superstitions, pseudoscientific claims, and everyday reasoning errors.
Components of the Fallacy
Sequential Events
For Post Hoc reasoning to occur, there must be two events, with one following the other in time.
Assumed Causality
A key characteristic of this fallacy is the unjustified leap from temporal succession to causality. The assumption here is if Event A precedes Event B, then Event A caused Event B.
Special Considerations
Statistical Correlation vs. Causation
A critical distinction in avoiding this fallacy is understanding that correlation does not imply causation. Rigorous scientific or statistical methods are needed to establish causative relationships.
Coincidence
Events can happen in sequence purely by chance. Proper analysis is required to determine if there is any direct link or if the events are coincidental.
Examples in Different Contexts
Economics
Claiming that a recession occurred because a government policy was enacted shortly before without evidence of direct causation.
Medicine
Assuming a patient’s recovery is due to a recently taken herbal supplement without clinical evidence demonstrating the supplement’s efficacy.
Everyday Life
Believing that wearing a specific jersey caused a sports team to win because it was worn during their last victory.
Related Terms
- Cum Hoc Ergo Propter Hoc: This fallacy assumes that if two events occur together, one must cause the other, regardless of their sequence.
- Post Hoc Fallacy vs. Slippery Slope Fallacy: A Post Hoc fallacy incorrectly infers direct causation from succession, while a Slippery Slope fallacy argues that one event will lead to another, typically negative and often extreme, event.
Frequently Asked Questions
Why is the Post Hoc Ergo Propter Hoc fallacy problematic?
It leads to false conclusions and poor decision-making by mistaking correlation or sequential occurrence for causation.
How can one avoid falling into this fallacy?
Apply critical thinking, seek empirical evidence for causation, and consider alternative explanations. Understanding the difference between correlation and causation is crucial.
References
- Logical Fallacies: A Guide to Critical Thinking by Alan Lightman.
- The Art of Deception: An Introduction to Critical Thinking by Nicholas Capaldi.
- Critical Thinking: Tools for Taking Charge of Your Learning and Your Life by Richard Paul and Linda Elder.
Summary
The Post Hoc Ergo Propter Hoc fallacy highlights a common pitfall in reasoning where simply due to one event following another, an illogical assumption is made that they are causally related. Recognizing and avoiding this fallacy is essential for sound reasoning, particularly in fields like science, economics, and daily decision-making. Understanding the difference between correlation and causation and demanding empirical evidence for causal claims can help mitigate the risk of such logical errors.
