There have been 4 main attempts at trying to repair the damage made to the tripartite theory be Gettier by introducing another condition to the triangle (making it a square).

The theories are as follows:

1. No False Belief Condition: Beliefs cannot be based on a false belief. This attempt argues that no knowledge can be claimed if it relies on a false belief. So, in our example, it is false that Fred is actually looking at Sam.

2. Causal Connection Condition: There must be a causal connection between the knowledge and the belief. This argument, first put forward by Alvin Goldman, states that a belief must have an appropriate connection to the knowledge claimed. In our example, Fred should not be able to claim that he knows Sam is in the room because there is no 'appropriate connection' between his viewing Tim (Sam's twin brother) and his conclusion that Sam is in the room.

3. Conclusive Reasons Condition: A reason must exist for the belief that would not be true if the belief itself were false. This was first put forward by Fred Dretske. If, for example, I believe that there is a chair in front of me, the reason for believing that it is there would not exist if the belief were false (that is, if the chair were not there).

4. Defeasibility Condition: Something is known as long as there is no evidence to the contrary. This is a common sense view, argued by Keith Lehrer and Thomas D. Paxson, which argues that Fred would be perfectly entitled to claim that he knows that Sam is in the room because he is not aware of anything to the contrary. Another example would be the flat earth theory, or the concept that the earth was the centre of the universe. These were once claimed as knowledge by the majority of people - until further knowledge arrived to prove that a different case.

Exercise

Are there any problems with any of the above theories? Take each in turn and see if you can think of how they might be criticised.