We would first like to thank those of you who commented on our editorial. The observations were both extremely interesting and cordially expressed. Nevertheless, we would like to clarify a small detail: the title “The exception does not prove the rule” paraphrases the statement “The exception proves that the rule is wrong”, made by Richard P. Feynman in the book entitled “The Meaning of It All”. Three of Dr Feynman's keynote lectures delivered in 1965 are included in this publication, which, curiously, did not appear until 1998 (Ed. Addison-Wesley), years after the death of the great physicist; apparently he was not fond of committing his ideas to paper. The phrase we quote is a simple statement that contradicts Cicero's original, and now popularized, declaration. In Feynman's view, if a rule is established, at least in physics and mathematics, it must always be true; a single exception to the rule proves that it is wrong. Exceptions or unexpected findings are only acceptable in a situation where multiple variables are in play. However, in physics (or any other science), a principle must always be met. R.P. Feynman may have been an eccentric who drove around in a truck adorned with his famous diagrams, but he was also one of the most brilliant physicists of the 20th century. For proof, we only need to look at the speed with which he determined the cause of the Challenger disaster, or the ease with which he used mathematical theory to crack the combination locks on the safes in the Los Alamos National Laboratory.

The real aim of our editorial was to reflect on the variability of clinical trial data that results from the endless number of uncontrollable variables in play, and to point out that this variability can at times undermine the strength of our conclusions. Perhaps it would not be a bad idea for medics to take a leaf out of the physics book.