Gettier Cases and Adept Belief



In his paper Manifest Failure: The Gettier Problem Solved John Turri proposes a definition of knowledge in response to Gettier cases.


Turri begins with some examples to help us understand a concept that he relies on his definition.


One of these examples involves contrasting two cases, labelled BOIL and FIRE.


(BOIL) You place a cup of water in the microwave and press start. The magnetron generates microwaves that travel into the central compartment, penetrate the water, and excite its molecules. Soon the water boils.


(FIRE) You place a cup of water in the microwave and press start. The magnetron generates microwaves that cause an insufficiently insulated wire in the control circuit to catch fire. The fire deactivates the magnetron and spreads to the central compartment. Soon the water boils.


Turri says that the outcome in the first case, BOIL, demonstrates the microwave’s boiling power, but the outcome in FIRE does not.


Turri defines knowledge as adept belief. More fully, you know proposition P if and only if you believe P and P is true and your believing P manifests your cognitive competence. (Much as the first case involves the boiling power of the microwave being manifested, so when you have knowledge your having a true belief is your cognitive competence being manifested.) Turri elaborates that cognitive competence covers any reliable cognitive disposition, power, ability, skill or virtue. He treats ‘manifests’ as primitive, based on our pre-theoretical understanding of it.


In Gettier cases, subjects believe the truth, but this does not manifest their competence. In Gettier cases, subjects suffer from bad luck that would normally prevent a true belief and then good luck, so that they nevertheless end up with a true belief. For example, here is Turri presenting a classic case:


(FORD) Sarah observes her trusted colleague, Mr. Nogot, arrive at work driving a new Ford. Nogot reports to Sarah that he is ecstatic with his new Ford. Sarah has no reason to mistrust him, so she believes Nogot owns a Ford. From this she infers that someone in her office owns a Ford. But Nogot uncharacteristically is playing a practical joke on Sarah: he doesn’t really own a Ford. Nevertheless, unbeknownst to Sarah, Mr. Havit, the newly hired clerk on his first day in the office, does own a Ford.


The microwave case is meant to parallel Gettier cases, because bad luck strikes disabling the magnetron, but good luck strikes and so the water is still boiled. One of the virtues of Turri’s account, is that it allows us to understand Gettier cases as part of a familiar pattern. We recognize the same thing happening in them as we recognize in cases such as FIRE. A second virtue he draws attention to is that “it deepens our understanding of knowledge by illuminating its relationship to other concepts fundamental to our way of thinking about the world, particularly manifestation.”



Turri, J. 2011. Manifest Failure: The Gettier Problem Solved. Philosophers Imprint 11: 1-11.