Suppose that John has never made a mistake. Today he plans to buy some low-fat milk at the store. By mistake, he incorrectly tells his friend Sara that he intends to buy whole milk. Later, when John goes to the store (still planning to buy low-fat milk) he accidentally picks up a container of whole milk. Not realizing his mistake, he pays for the milk and leaves the store. 

Does Sara know what kind of milk John bought at the store?
If Sara were asked this, she would say that she knows that John bought whole milk. 

✓ Notice that Sara is indeed justified in thinking that John bought whole milk. 

✓ It also is true—though by accident—that John bought whole milk. 

✓ So, Sara has a justified true belief. 

Nevertheless, most would all agree that Sara doesn’t really know that John bought whole milk, because Sara’s belief was based on a[n initial] falsehood. 

One might be tempted to say that it doesn’t really matter what theory of truth one holds, or what truth even is: what does it matter? 

In fact, the parties to these debates are fighting over matters that directly affect each of us.

What differing outcomes do you arrive at when you apply each of the three theories to different cases? 

If they produce different results as to what constitutes truth, then it matters which theory you accept to determine what counts as ‘reality’ and ‘knowledge’ 

Science & Truth:

Many people hold that science clearly gives us the truth about the world. 

They may be thinking of all of the successes of science (e.g., curing hundreds of deadly diseases, putting people into space / on the moon, & creating media for virtually instant communication over thousands of miles).

However, science itself never rests upon past experience and is always open to new evidence. A marker of good science is willingness to revise belief / hypothesis in light of such new information.