Speaking of Wikipedia (and Gettier Problems)...

The Cow in the Field

Farmer Franco is concerned about his prize cow, Daisy. In fact, he is so concerned that when his dairyman tells him that Daisy is in the field, happily grazing, he says he needs to know for certain. He doesn't want merely to have a 99 percent probability that Daisy is safe, he wants to be able to say that he knows Daisy is safe.
Farmer Franco goes out to the field and standing by the gate sees in the distance, behind some trees, a white and black shape that he recognizes as his favorite cow. He goes back to the dairy and tells his friend that he knows Daisy is in the field.
Yet, at this point, does Farmer Franco really know it?
The dairyman says he will check too, and goes to the field. There he finds Daisy, having a nap in a hollow, behind a bush, well out of sight of the gate. He also spots a large piece of black and white paper that has got caught in a tree.
Daisy is in the field, as Farmer Franco thought.
But was he right to say that he knew she was?
The philosopher, Martin Cohen, who described this scenario originally ^[1], says that in this case the farmer:

• believed the cow was safe;
• had evidence that this was so (his belief was justified);
• and it was true that his cow was safe.

However, we might still feel that the farmer did not really know it. Herein lies the core of the problem of 'knowledge as justified true belief'.

Source: http://en.wikipedia.org/wiki/Gettier_problem

The Gettier Problem reading from class can be downloaded from our class page on the Source.