This article first appeared on Scientia Salon
Philosophers have traditionally defined “knowledge” as a belief that is both true and justified, a definition that sufficed until, 50 years ago, Edmund Gettier pointed out that the conditions could be fulfilled by accident, in ways that didn’t amount to what we would intuitively regard as “knowledge”.
Gettier pointed to scenarios such as:
“Smith has applied for a job, but, it is claimed, has a justified belief that “Jones will get the job”. He also has a justified belief that “Jones has 10 coins in his pocket”. Smith therefore (justifiably) concludes that “the man who will get the job has 10 coins in his pocket”. In fact, Jones does not get the job. Instead, Smith does. However, as it happens, Smith (unknowingly and by sheer chance) also had 10 coins in his pocket. So his belief that “the man who will get the job has 10 coins in his pocket” was justified and true. But it does not appear to be knowledge.”
Since Gettier’s paper many attempts have been made to patch up the “justified true belief” definition, often by adding extra conditions aimed at ruling out being right accidentally, though none of the proposed solutions has gained general acceptance and most have been shown not to work.