In the study of knowledge we distinguish between knowledge by acquaintance, in essence to know someone or know of something. Ability knowledge is for example to know how to swim or how to ride a bike. And, our main concern, propositional knowledge that is sentences or statements that can be either true or false. To have knowledge one needs to have a belief and for this belief to be true. The following text will show how true belief, even if it is justified in a rational way, does not suffice for knowledge.
Take Nina, she is walking by some slot machines in the casino. She feels drawn to one of the machines, and believes it is her lucky day and that she will win because of the nice appealing colors on the slot machine. She places her bet, the wheels spin and line up three lucky 7’s, she wins and her belief turns out to be a true one. But while her belief being true, intuitively this do not suffice for knowledge, as it is easy to ascribe this winning to pure chance.
Even if different suppositions may justify Nina’s belief in winning, it is natural to think that what Nina lacks in this situation to have knowledge, is justification. And also for this justification to be strong enough for Nina to be a rational being in believing she will win, without need to turn to superstition or vagueness to explain her belief. But even if Nina where to have a justified true belief, which she formed in a rational way, it is easy to show that this neither suffice for knowledge.
Say Nina is a con girl, she has tricked the manager of the slot machine manufacturer to give her a manual, showing all the results the machine can produce, together with a serial number for each spin which is also displayed on the slot machine. So it is easy to look down in the manual what the next result will be. It is noon and Nina is now standing in front of the slot machine in the casino. She reads the serial number in the display and matches it in her manual.
The next spin will line up three lucky 7’s and win. She places her bet and spins the wheel. Unbeknown to Nina there was an error when printing the manual so all the numbers are mixed up, making the manual useless. And this day the casino owner celebrates his 60th birthday by letting all the machines go off program at noon and give every placed bet at that time the three lucky 7’s line up. Nina’s justified belief turned out to be true, but due to lucky and unlucky circumstances we do not ascribe knowledge to Nina in this situation.
Nina was responsible and rational when forming her belief, considering she went the length to trick the boss to give her the manual to see which spins win. If her goal is to win at slots, she was responsible when gathering evidence and responsible and rational in believing her evidence.
And even if this example showed that an agent with a justified true belief formed in a rational and responsible way, do not necessarily have knowledge. It is easy to see that even if the agent lacks knowledge, she will often be successful in reaching her goals, because of the rational way she gains justification for her beliefs. Though it is not sufficient or may not even be necessary to have justified true beliefs when trying to grasp the nature of knowledge.
Pritchard D. (2006) What is this thing called knowledge?, Routledge, Oxon