Justifying a reason that entitles you to a belief is inadequate. It is not enough to claim belief in something only because you wish it to be true. Conversely, wishing for something doesn't necessarily demonstrate belief. If there are sufficient reasons to have a wish justified by a belief that is based on evidence, we call that being rational. But if your knowledge is a rational belief purely based on physical evidence, could you still be wrong? Surprisingly, the answer is yes.

Let's go over a quick example that only a goodhearted skeptic would point out: Suppose I'm expecting a customer in the store any minute. You tell me a customer has arrived at the door, yet you are trying to deceive me. It just so happens a customer arrived at the exact moment of your attempted deception. In this case, my belief is true. I have good reason to believe it's true since you told me so, and you have a reputation for honesty. But I don't know with absolute certainty the customer has arrived since it was only an accident that I got it right.

The entire idea behind what we claim as knowledge has myriad conceptual limitations, and we should always think carefully and systematically. Correct beliefs aim at objective truth . Truth is the primary thing beliefs are required to be if they are to add up to knowledge.