‘Post hoc ergo propter hoc‘ — don’t make this blunder!
Modern English is replete with confusing Latin phrases; however, they do seem to be an interesting way of emphasizing an idea and giving it special status. This example is a specific case of logic where the term ‘post hoc ergo propter hoc’ represents a seemingly innocuous fallacy that creeps in without us putting an absurd Latin label to it. But what exactly is ‘fallacy’? It is defined as an error in reasoning for the claim that is superficially logical but is not correct upon deeper inspection. Coming back to ‘Post hoc ergo propter hoc’, in the crudest translation it means ‘after this, therefore because of this’. It is easy to fall into the thinking trap for correlated events. Whenever we conclude that since event ‘i’ happened before ‘j’, so ‘i’ caused j, we may be committing this logical error. Even if two events have occurred consecutively, it does not imply that the previous one has caused the next one.
It is a common belief in some countries that if a cat crosses the road then it becomes inauspicious to move forward and break the ‘virtual line of crossing’. Some people believe that sneezing while leaving home may lead to a bad day. Similarly, some may assume that they have a ‘lucky pen’ for the examination and they attribute the results to the pen. What is even more interesting is that it is not just novices who fall for the trap, there have been legends who believed in such notions. The example of football star Pelé is commonly known. The football star once gave his shirt to a fan and saw a decline in his performance. He assumed that giving the shirt caused him to play badly. He immediately set a friend with the task of retrieving the same. He made it clear that he needed it at any cost. Subsequently, he got back the shirt. Lo and behold, he was back in form within a week! Talk about the lucky charm effect. This evidently reinforced his belief in his ‘lucky shirt’. However, it was later revealed by his friend that he simply gave him his new ‘unlucky shirt’ after a failed attempt at finding the old ‘lucky one’. There are lesser but even more bizarre ways of rituals that footballers have practiced like listening to specific songs before the match, keeping an even number of items in the fridge to even urinating in the leftmost urinal or urinating when the washroom is empty, the list goes on and on.
There are some other common life examples of this phenomenon. If you give your car to your friend and he returns it next day. Sadly for you, the car breaks down ten minutes into your drive. You may attribute the break-down to the friend and think that it was caused by him. Possibly he could have used it in a rash manner. However, there could be finitely other possibilities which would not be dependent on the event of the car being used by someone else. Similarly, someone moves into a new house and next month, she is laid off from the job. After a few days, her kid falls ill. These events could make her believe that there is some ‘bad spell’ in the house which leads to the bad occurrences and she could think that shifting to the new house has caused these troubles. This kind of the wrong attribution of the events can be found everywhere around us. We are so used to them that it would not raise an eyebrow. Many of us may believe in them too. It is not all lost until it is limited to personal lives, however, it becomes a major concern when it creeps into the analysis for on a professional level. The very nature of two events occurring in succession could drive us to believe that first event has caused the second. The chronological sequence is misleadingly taken as causality in many cases. Many times, we adults, and even more embarrassingly, as researchers, we commit a similar mistake. There are numerous studies where the researcher may jump to conclusion using statistical tools which show a very high correlation between two events and believe them to be causation. The fallacy of ‘post hoc ergo propter hoc’ also called ‘post hoc’ is due to the attribution of causality simply because of the order of the occurrence of the events rather than consideration of the antecedents for the second event. With a better inquiry, we may possibly rule out the event 1 as one of the consequents for event 2. There are many ways to test this, however, it all begins with the researcher.
The reasoning that we may have for knowledge about some event may be a priori or a posteriori. The Scotland yard found a dead body beside a river. We know for sure that if the death is caused due to unnatural means like stabbing then it would have been a result of murder while on the other hand to know the time of death, we need an autopsy to analyze the body and come to conclusion about it. The statements that are of the first type may be derived purely from the logical derivation while for the second type we need empirical verification.
“Although all our cognition begins with experience, it does not follow that it arises [is caused by] from experience”- Immanuel Kant.
Finally, an easy process to avoid having the post hoc ergo propter hoc fallacy is to not take the causality at face value of two consecutive events A and B. Firstly, think of a ‘logical’ explanation for the statement that ‘how exactly A causes B? Apart from the occurrence of an event, is there any explanation for this? Usually, the causality can be logically explained if it is there. We could test for some intermediate steps between A and B. Consider the same person in the house example. She was told by her manager that she was fired because she was frequently late to the work. When she sits down, she remembers that her old house was near to her work while the new one is far away with uncertain delays in traffic. Could she then attribute that her moving to new house lead to her firing? Also, another great way to eliminate such statement is the use of control based causation. In a number of replications of the event, we need to observe the occurrence of both events. If we assume that A has caused B, we could see that whether there are cases where B does not follow the occurrence of A. As with any empirical validation, we are essentially trying to find support for invalidation of the assumption of ‘causal relationship’ from A to B and we need to be careful as it may be that after ’n’ number of observations, we may find our black swan.
