Let's quickly review our line of belief and how we define these terms for the purpose of this discussion:
Skepticism is following the evidence wherever it leads. Denial is refusing to believe no matter how compelling the evidence is. Credulity, therefore, is believing in something no matter how compelling the evidence against it is.
Some people need to (or think they need to) believe. The easiest place to see that is with religion. It doesn't take a lot of rational thought to realize that not every religion can be true and that most traditional religions require belief in things that are highly improbable. Yet people persist in these beliefs no matter the evidence against. They want to believe. They need that belief in order to cope or make sense of their world.
The same is true in politics. Consider those who take a hard line regarding their politics. Typically, they'll cling to the candidates and positions that are approved by the party with little to no regard for the truth. In fact, if you present people with evidence against their beliefs, they are likely to dig in further and cling even tighter to their position.
Of course, both of these examples are stereotypes. There are many people in the world who do have more nuanced views or are skeptical of some things. In fact, most of us can be at any position on this line depending upon the subject matter. Let's look at some other ways in which every day credulity can be misleading or harmful.
There are some people who believe that UFOs are alien spacecraft and that we've been visited before. Some folks even believe that our world is already being guided (or maybe has been invaded) by these creatures. They believe this so strongly that every odd occurrence, every single anomaly, becomes confirmation of their belief. And no matter what rational evidence or sound explanations you provide, they will dismiss you as part of the cover-up or simply blind.
The same goes for most any conspiracy theory whether it be regarding the Illuminati, the New World Order, the JFK assassination, communist/socialist takeover, fad diets, detox, homeopathy, or other junk. There will always be those credulous people out there who cling to something outlandish and unproven to make sense of their world. Dare to challenge them and, at best, you'll be accused to being part of the conspiracy. Laugh at the idea of the NWO and you'll hear something like, "You're blind to it now but wait and see. You'll wish you'd listened to me when they take control." Challenge someone's ideas about detox or alternative medicine and they'll accuse you of being paid off by "Big Pharma."
The problem here is not that people believe something that's untrue so much as that they believe it so strongly that they simply cannot question it or allow you to question it. It has become dogma for them and is no longer open for debate. They may waste their time, money, and energy on these ideas with little or no obvious harm yet, as these unsubstantiated ideas spread, the more time, money, and energy gets wasted on them. Eventually, they may reach critical mass where they become like politics and religion - belief systems in which each person is absolutely sure s/he has the right answer and to hell with anyone who dares to disagree.
How do we find that healthy point of skepticism? It's not always easy. Every one of us has beliefs that we cling to ferociously whether they were taught to us from childhood or whether we developed them on our own. Some of these beliefs make up our core identity and, as such, are difficult to challenge. But that challenge is precisely what we face if we wish to be people of truth. For if we can learn to be skeptical of the things we think we know best, then we will have retained our ability to learn, to be flexible, and to be humble before the vast body of knowledge that exists in this world.
From my own past, I must admit that I was a very credulous child. I believed 100% in Christianity, in the supernatural, in ghosts, angels, fairies, UFOs, aliens, Nessie, and Bigfoot. I believed anything and everything I was told because: 1) I wanted to believe it, and 2) I was taught to trust adults unquestioningly. It took me many years to apply my skepticism to these things and, believe me, it was difficult. It hurt. It was a little scary and very disheartening. I thought my world was going to be dull and dreary if I accepted that this stuff probably doesn't exist.
Instead, I find out that reality is much richer than I ever could have imagined. I count myself fortunate to have gotten out of credulity and into skepticism. Now I don't feel like I'm wasting my life fantasizing about what can never be true. Instead, I'm delving deeper into what is demonstrably true and I'm loving it!
Ask yourself today what pet beliefs you hold that need to be challenged. You might be amazed. After all, we are presented with tons of information everyday (thanks to TV and the internet) and we need some way to separate fact from fiction. How do you do it? How do you know you're doing it right?