How deductive reasoning can lead us to stupid conclusions

“Elementary, my dear Watson… “

Let’s say you are a researcher hard at work analyzing results from your current medical project. You have a large number of available options that may affect the results of that research before coming to any published conclusions. (And if Big Pharma is funding your research, you likely have considerable motivation to skew those results to favour their product). What you will certainly be most interested in is simply interpreting your existing data by applying deductive reasoning to come up with “The Truth”. In other words, what are you going to tell the world that your findings mean? But according to the clever scientific minds over at Photon In The Darkness, deductive reasoning is not all it’s cracked up to be:

“Deductive reasoning is defined as ‘an argument where the conclusion is a logical consequence of its premise’. Many believe that if their conclusions follow logically from their premises, then their conclusions must be true. But this reasoning can be either valid (if the conclusions are logical consequences of their premises) or invalid (if they are not).

There is no true.”

In an essay last year called Deductive Mis-Reasoning,  filed under their Help For The Bewildered section, Photon In The Darkness offers us the perfect simplistic example of flawed deductive reasoning at work: the iconic fictional police detective, Sherlock Holmes. Continue reading