In 1963, Edmund Gettier argued justified true belief (a belief that is justified and happens to be true) is not necessarily knowledge. According to Gettier, for a belief to be knowledge, it must satisfy three conditions:
1. it is believed
2. it is true
3. the believer’s belief must be reasonable*

*another complicated issue

“The Cow in the Field,” a scenario first told by philosopher Martin Cohen:

A farmer asks his dairyman if Daisy, his cow, is indeed in the field. The dairyman assures the farmer that Daisy is safe in the field. But the farmer still isn’t entirely satisfied—he’s pretty sure, based on what the dairyman said, that Daisy is safe, but he want to know for sure. So he goes to look for her in the field, standing just outside the farm, facing the field where she supposedly is. He sees a white and black shape in the distance and recognizes it as Daisy.

The question is whether the farmer really knows Daisy is in the field, whether Daisy being in the field is belief or knowledge.

To double check (or triple check or whatever), the farmer has the dairyman look one more time. So the dairyman goes into the field and finds Daisy taking a nap. He also sees, in the spot where the farmer thought he saw Daisy, a huge piece of black and white paper caught in a tree.

The dairyman was right the first time around, but was he right based on knowledge, or was he just right in belief? In other words, did he, at first, know Daisy was safe, or did he just believe> it?

1. The farmer believed the cow was safe.
2. The farmer had evidence she was safe; he (thought he) saw her in the field.
3. The cow was safe the whole time; she was napping in the field.

But the farmer did not know Daisy was safe; his belief just happened to be true knowledge. In this case, belief and knowledge were the same, even though the belief was based on faulty evidence. Therefore, there is the problem of “knowledge as justified true belief”—whether a belief, just because it can be justified and happens to be true is actually knowledge, or just a belief that conveniently aligns with knowledge.