The Tripartite View

Plato's tripartite definition of knowledge

A subject knows that a proposition is true if and only if a subject believes that the proposition is true, the proposition is true, and the subject's belief that the proposition is true is justified. 

Individually necessary

The conditions are all needed to satisfy the conclusion.

Jointly sufficient

Together the conditions are enough to satisfy the conclusion.

Gettier Case

Smith has strong evidence (the president has told Smith that Jones will get the job) that Jones will get a job and knows (JTB (has seen them 5 minutes before the interview)) that Jones has ten coins in his pocket. From this, Smith infers: “The man who will get the job has ten coins in his pocket.” He believes this and is justified. However, Smith himself (unknown to him) has ten coins in his pocket and he gets the job. His belief is therefore true and justified, but true only by luck. So Smith has a justified true belief, but not knowledge. 

Infallibilism

A subject knows that a proposition is true if and only if a subject believes that the proposition is true, the proposition is true, and the subject's belief that the proposition is true is infallibly justified (the proposition is indubitable). 

How Infallibilism beats Gettier cases

Beats Gettier because Smith was not infallibly justified to believe that Jones will get the job. 

No False Lemmas

A subject knows that a proposition is true if and only if a subject believes that the proposition is true, the proposition is true, the subject's belief that the proposition is true is justified, the subject's belief that the proposition is true is not based on a false lemma. 

How No False Lemmas beats Gettier cases

Beats Gettier because the lemma that the president is telling the truth is false. 

Reliabilism

A subject knows that a proposition is true if and only if a subject believes that the proposition is true, the proposition is true, and the subject's belief that the proposition is true is formed by a reliable cognitive process. 

Reliable cognitive process

A process which produces a higher proportion (over 50%) of true beliefs (eg sight). 

How Reliabilism beats Gettier cases

Beats Gettier because hearing someone lie is not a reliable cognitive process

Epistemic Virtue Knowledge

A subject knows that a proposition is true if and only if a subject believes that the proposition is true, the proposition is true, and the subject's belief that the proposition is true is a result of exercising epistemic v

Epistemic virtues

Particular skills, abilities or traits that contribute to someone getting to the truth. They are the processes and qualities that are more likely to yield a higher rate of true belief.

How Epistemic Virtues beat Gettier cases

Beats Gettier because Smith did not use an epistemic virtue.