Word Play: Believing
–verb (used without object)
1. to have confidence in the truth, the existence, or the reliability of something, although without absolute proof that one is right in doing so: Only if one believes in something can one act purposefully.
–verb (used with object)
2. to have confidence or faith in the truth of (a positive assertion, story, etc.); give credence to.
3. to have confidence in the assertions of (a person).
4. to have a conviction that (a person or thing) is, has been, or will be engaged in a given action or involved in a given situation: The fugitive is believed to be headed for the Mexican border.
5. to suppose or assume; understand (usually fol. by a noun clause): I believe that he has left town.
"Believe" crops up in the context of this 'blog because of the disparate ways in which people have validated the assertions that they make.
In my business, "believe" is used in the sense of definition 2, with the additional caveat that our confidence in the truth of some statement is based on examination and understanding of the data used to support that statement.
Thus, when I say, "I believe in the Theory of Evolution.", I am not expressing a religious faith (as the Creationists/Intelligent Designers would have you think), but am stating:
"I have examined the theory of evolution and have found it consistent with the available data from current life and the fossil record"
It's just shorter to say that I "believe" it.
Another way in which some people use "believe" in the realm of science (as opposed to religion, where definition 1 would be entirely appropriate) is to indicate that they trust the source of their information such that they are willing to accept it without actually understanding it. In essence, they are simply "parroting" what they have been told.
Now, most of the people who are acting as "parrots" don't see it that way. They are usually convinced that they understand the topic quite well enough to see that their assertions are correct. They assume that a superficial - and usually over-simplified - understanding of an issue can make them equal to people who have studied the topic in depth.
To some extent, this belief (definition 1) that "everyday people" can understand a topic as well (or, in some instances, better) than the "experts" is a lingering zeitgeist of the 20th century, epitomized by many in the "Baby Boomer" generation (my generation, regrettably). It is, unfortunately, no more a reflection of reality than most of the philosophical nonsense to come out of that generation.
Moral philosophy, no matter how good it makes you feel, never trumps reality. The Soviet Union had to learn this lesson the hard way (see: Trofim Lysenko) and it appears that many in the Western World are determined to repeat their mistakes.
No, as much as we might like it to be different, there is no substitute for actually learning the subject. Reading "Molecular Biology for Dummies" will not put you on par with someone who has put in the hours and effort required to really learn the subject. This is not to say that people with lots of education and advanced degrees cannot be wrong - that is most definitely not true (see: cold fusion)! However, when discussing their field, the smart money is betting on the "expert" over the "self-educated".
So, why is it that so many people think that they know more about, say, autism and mercury than the people who have studied it for decades? For the answer to this question, we have to go to the source - literally.
These days, it is considered indelicate for a doctor or scientist to say (or imply) that a topic is too complex for the "public" (i.e. the "average" person) to understand. This despite the all too obvious fact that many - if not most - topics in science have grown too complex even for scientists outside the field to fully grasp. The "average" person, with at most a semester or two of college science, hasn't a chance.
As a result, people read about some aspect of biology, chemistry or physics in Scientific American and think that they can intelligently discuss the matter with someone who does research in the field (true story). And in situations where the source either doesn't have a full grasp of the topic or has a personal reason to over-simplify the matter (actually, those two aren't mutually exclusive), the potential for deception - intentional or not - is extreme.
For example, there is currently a belief that the GnRH agonist, leuprolide (Lupron) will help autistic children. On the part of the people originating this idea, the belief (definition 2) in Lupron's effectiveness is based on two other beliefs (definition 2?):
 Autism is caused by mercury toxicity
 Testosterone and mercury form a complex, with sheets of testosterone surrounding mercury atoms
The validity of belief  is very doubtful at present, but belief  is valid - with one caveat:
The complex of testosterone and mercury has only been seen when equimolar amounts (equal number of molecules of each) were mixed with the minimal amount of hot (50 degrees C, about 120 degrees F) benzene.
Now, it is entirely possible that the people who started this idea are unaware of the little caveat above. But I'd be willing to bet a largish sum that the people who are parroting the "lupron helps cure autism" claim are completely unaware of it. Yet it is information that is freely available...if you can understand it.
So why do I worry about people repeating nonsense they don't understand?
A large part of the problem with the parroting of bad (or unsubstantiated) information is that people - so the psycholgists tell me - tend to give credence to things they hear from numerous other people. "Everybody's saying it, so it must be true!" Such tempting logic, but false.
This same sort of "logic" crops up in the various autism polls, surveys and questionaires that litter the Internet. The folks running them must believe (definition 1, I suspect) that a collection of "average people" will generate an above average understanding of the topic. The myth of the "wisdom of the common man" is repackaged as the myth of the "wisdom of common parents".
Don't get me wrong; I think that parents know a lot about their kids - I know a lot about mine. I also know a lot about my car, but I don't think for a moment that I understand its inner workings better than my mechanic. I still get peeved when she can't find the rattle or shimmy that I describe, but I don't think that I know more about how my car works than she does.
In the end, scientific "fact" has traditionally shown no respect for opinion polls. No matter how many school children want Pi to equal 3, the mathematical relationship between a circle's radius and circumference remains obstinately the same (3.14159...). And even majority support on the school board won't make "Intelligent Design" a valid hypothesis - let alone a theory. The same will happen with polls and surveys about the cause of autism - no matter how many people "vote" for mercury, the facts will remain unchanged.
You can choose to believe that or not.