There's a difference between paranoia and skepticism. Actual paranoia is an irrational belief that people are engaged in some act or acts with nefarious intent, where skepticism is a doubt about the veracity or accuracy of a statement. An irrational belief is a belief that isn't falsifiable. If someone tells you that NASA is engaged in a conspiracy to trick the world into believing the Earth is round you have the first element of paranoia, but not the second. If you ask them, "What evidence could be unearthed to convince you otherwise?" and their answer is that there is no possible evidence that could convince them otherwise, then you have the second element. In summary, their belief meets both criteria of paranoia: 1. A belief that an actor or actors are planning or carrying out a coordinated plan with nefarious intent. 2. The belief is not falsifiable. A skeptic just has a doubt that is completely reversible in the face of evidence. If you say, "I'm not sure the Earth is round," and are willing to accept evidence that it is round, you are a skeptic and not a paranoid.