The questionable cause fallacy, described by the Latin phrase cum hoc ergo propter hoc, is an error of thought which leads us to believe that one event causes another event simply because the two events occur simultaneously. This error can easily be reinforced if the simultaneity of the two events is often repeated.
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One of the greatest conquests of human knowledge is the principle of causality, which says that all phenomena in the universe have a cause. This principle forces people who truly love the truth to look for the real causes of phenomena—that is, to explain them. They expect scientific theories to also have a justification: not only answering the “How?” question, but also the “Why?” question. Therefore, to be a rational being, man must apply, in all circumstances of life, the principle of causality. This assures him that he has authentic knowledge and is able to make appropriate decisions.
Why is it important to know what causes things around us? Because, based on this knowledge, people can produce desired outcomes, and move from the realm of necessity into the realm of freedom. This was the basis of the modern idea of freedom, which Dutch philosopher Baruch Spinoza (1632-1677) defined as “understood necessity”. By understanding causation properly, and what actions to take based on this understanding, people “humanise” the world around them, turning necessity into freedom.
This is why we must be vigilant in certain situations so that we can identify the danger of the questionable cause fallacy, either in other people’s thinking or our own.
Superficial logic, and the absence of training
When a correlation-causation fallacy is combined with superficial logic and an untrained mind, it can lead to superstition, prejudice, or obsession. For instance, a man declares that every time he watches the football team he supports, lying in bed, leaning against three pillows, his team wins. When he does not watch in this exact way, his team loses. Similarly, someone claims that if you start reading the Bible and do not finish it, you will suffer. There are people who are obsessed with numerology and believe that all even numbers they came across are beneficial, while the uneven ones are detrimental. Others have claimed that the biblical Psalms conjures negative energies, because they sometimes contain curses. Of course, all these errors relate to the questionable cause fallacy, and have repercussions on the decisions made by those who fall into this fallacy.
The absence of essential data to prove causation
The questionable cause fallacy can be related to the small sample fallacy, as well as the hasty generalisation. Other times, essential data to establish if a certain phenomenon is the real cause of another phenomenon are not accessible. For instance, as French anthropologist Claude Lévi-Strauss pointed out, someone who has a snake fall on their head when they pass under a certain tree could believe that, each time he passes under that tree, the phenomenon will repeat itself.
In ancient times, because what caused the different phases of the moon was unknown, it was believed that the moon diminished in the sky because it was periodically eaten away by werewolves, and was afterwards restored.
Other times, certain theories regarding the causes of certain phenomena are challenged by new knowledge. For instance, in the past century the medical world believed that both animal and plant proteins were equally healthy for the human body. However, recent studies have shown the superiority of plants as a source of protein for one’s health.
This fallacy often occurs in people who incorrectly analyse data from polls or scientific studies, seeing causal relationships where there are only coincidences, or merely correlated phenomena. Sometimes, the error is one of reverse causality, when two events really are in a cause-effect relationship, but the result is mistaken for the cause (for instance, a broker thinks he should invest less into a certain company due to a lack of results, when, in reality, the lack of results was generated by the low investments). We must take into account that where a scientific study does not mention a relation of causality, we have to make do with mere correlations. Many phenomena can be correlated, and observing these correlations should prompt us to deepen our study in order to understand their actual causation.
Do we think about causation correctly?
Besides identifying the questionable cause fallacy in others, let us ask ourselves: do we always know when we’re dealing with a real cause and when we’re dealing with an apparent cause? This does not refer to the objective possibility of knowing causes, because that does not depend on our thinking, but on the concrete state of the knowledge available to us at a given point in time. We are referring now to thinking errors which can get in the way of objective knowledge. In what circumstances is the cause we’ve identified a mere correlation between two phenomena, a simultaneity relation, or a coincidence?
The Scottish philosopher David Hume pointed out, in An Enquiry Concerning Human Understanding, that the influence of habit is crucial. Where habit is at its strongest, it not only hides our natural ignorance regarding the true relation of causality, but it also hides itself.
The issue we are discussing—the questionable cause fallacy—emerges out of habit, out of simplified, convenient thinking, which numbs our critical abilities. Noticing this thinking error in our lives should serve as a wake-up call to cultivate our critical and autonomous thinking.
In a nutshell
The questionable cause fallacy is related to the hasty generalisation and the small sample fallacies. The Latin version—cum hoc ergo propter hoc—points to the error of someone believing a certain event to be the cause of another just because it happened at the same time as the first, and the simultaneity of the two is mistaken for a causal relationship.
It is common error for untrained minds to commit. When we think based on habit, or have fallacious logic, prejudices, or a tendency to be superstitious, we disrupt the natural logic of the mind. Thus we often hear around us: “If you sweat, it means you have a fever”; “Each time you see the priest, something bad will happen to you”; “I don’t lend money because it brings me bad luck in business”; “Whomever tries on another girl’s wedding dress will never get married”, and so on.
Enhance your critical thinking. Read more of our articles on the topic.
Dumitru Borţun is a university professor at the Faculty of Communication and Public Relations, part of the National School of Political and Administrative Studies (SNSPA).