The detective: between logic and chance
When we think of Sherlock Holmes, we picture the famous detective solving the mystery from the comfort of his home, never stopping smoking his pipe or spilling a drop of his Ceylon tea, thanks to his prodigious brain. There is nothing of luck in his implacable, cold logic… in appearance.
The term serendipia comes from the English serendipity. It is no accident that it sounds better in Spanish than in English, considering that it comes from serendip, a word of Arabic origin like so many others of the same origin that have enriched the Spanish language. The English writer and politician Horace Walpole coined the word serendipity in honor of the tale “Three Princes of Serendip” more than 250 years ago. The kingdom of Serendip that gives rise to the tale, today Sri Lanka or Ceylon, is an island south of India. In the story, three princes are unjustly accused of a theft after having deduced multiple qualities of certain stolen objects. I will not give more details so as not to ruin an entertaining story that I recommend reading. The word serendipity ended up denoting a “fortunate and unexpected discovery achieved while looking for something different,” or, as we would say more informally, a lucky fluke. Cited as examples of serendipity are the discovery of Penicillin, of post-its, Archimedes’ principle and Teflon, among others.
However, in the tale of the three princes of Serendip, luck does not intervene: the brothers describe the qualities of the stolen items through a process of deduction not very different from the one other famous detectives would use. Moreover, some claim that this tale was a source of inspiration for Voltaire in his novel Zadic, which in turn could have inspired Edgar Allan Poe for “The Murders in the Rue Morgue,” starting the detective novel genre.
From this same tale, then, two opposing dimensions emerge: on one hand, luck and, on the other hand, logic. The dissonance is only apparent. Let us consider an excerpt from “The Hound of the Baskervilles”:
We are coming now rather into the region of guesswork -said Doctor Mortimer.
Say, rather, into the region where we balance probabilities and choose the most likely. It is the scientific use of the imagination, but we have always some material basis on which to start our speculation.- replied Sherlock.”
The Hound of the Baskervilles — Arthur Conan Doyle.
Sherlock (and every good detective) knows that for the same evidence there can be multiple explanations, some more plausible than others. Probabilities let him know which is the most likely cause, and new evidence lets him confirm or discard some of the hypotheses. It is the scientific method in its full expression.
Suppose that for a crime there are 4 possible culprits with a certain estimate of guilt considering the current evidence: Alicia (24%), Bob (24%), Carlos (49%) or David (3%). We would no doubt be inclined to believe that Carlos is the culprit since he has more than twice the probability of the other 3 suspects. However, it is more likely that he is not guilty (24%+24%+3%=51%) than that he is (49%). Of course, we still cannot prove Carlos’ guilt, but the most reasonable course of action is to investigate Carlos more deeply to confirm or refute the hypothesis of his guilt. If more evidence is finally found and we are right that Carlos was the culprit, we must then admit that we have had a degree of luck, since other scenarios were also admissible (even more probable). It is the mix of deductive analysis, directed search and luck that ultimately leads to success.
In short, there is serendipity or luck in the deductive process. Although the most likely option is chosen through logic, and the investigation continues on it until possibilities are exhausted, there is some luck in the initial explanation being the correct one, rather than other less probable ones (with the initial information), and in the discovery of new clues and evidence.
As Louis Pasteur said: “Chance favors the prepared mind”.