.." (Simon Blackburn) To qualify as knowledge, belief must not only be true and justified, the evidence for the belief must necessitate its truth.

Richard Kirkham)

What you say: Since 1963 when Gettier's article was published, many other articles have come out trying to come up with an adequate definition of knowledge. Some of them have tried to supply a fourth condition. These are just a couple of possibilities.

Another possibility for a fourth condition of knowledge is that the justification be undefeated. There should be no overriding truths that defeat the reasons that justify a person's belief. For example, suppose Sam believes Tom Brown stole a book from the library. He justifies this claim because he saw Tom Brown steal the book from the library. Something that would override or defeat this claim could be a true proposition like "Tom Brown's identical twin Paul is currently in town.

If no such defeater exists, then the belief is justified.

Slide 4: What is Belief?

In order to know something, we must think it is true.

What you say: Sometimes you'll hear people say something...

This is not what epistemologists mean when they speak of belief.
A belief is something you think is true.

Knowledge is distinct from belief and distinct from opinions. You could believe something and find out you were mistaken, but the same cannot be said for knowledge. For example, suppose Jim believes the bridge is safe, drives his car across it, and the bridge collapses. We would say Jim believed the bridge was safe, but his belief was mistaken. We wouldn't say he knew the bridge was safe because obviously it wasn't. To count as knowledge, what we believe must be true.

Slide 5: Knowing that... And Knowing how The ability to do something and the ability to describe how to do something

What you say: The ability to actually do something and the ability to describe how to do something are two different kinds of knowledge. For example, a person might say, "In order to drive a car with a manual transmission, you have to change gears by putting your foot down on the clutch and moving the gear shift from one position to another."