If the scientists in a particular field pretty much agree on something, and you are not in that field, you have no business disagreeing with them. It is not rational for you to disagree with them.
I know the common objection-- that science has been wrong many, many times before. This is true. In fact, I believe that much of what we think we know about science now is probably wrong to some degree. However, we don't know what things are wrong and what things are right, and the things we know are wrong we have no better ideas for.
But even if 80% of the scientific "facts" of today turn out to be wrong, it's still rational right now to believe them, and to act as though they are true. This is because science is the best way to get at knowledge about the world, and science's best guess at something is certainly going to be better than yours. When science comes up with a better idea, then it's rational to change your mind.
I was teaching a class last semester and told the class the results of some scientific study. A student said "I don't know about that; my sister--" I cut her off.
"You're not about to argue against a scientific finding with an anecdote, are you?"
"No," she backed down.
Most people want to disagree with scientific findings based on their own personal experience. But anecdotal evidence is terrible. Science is a better way. If you want to disagree with science, you have to get the study and find out what is wrong with it.
Now I'm a scientist, but even I cannot rationally disagree with the consensus of findings in other fields. Climate scientists think global warming is caused by people? Okay. Time started with the big bang? Okay.
I can only rationally disagree with stuff in my field, about which I know a great deal.
What's interesting to me is that disagreeing with the status quo is good for science. If scientists don't come up with crazy theories, we won't make any progress.
Let me re-phrase that-- scientists disagreeing with the status quo in their field is good for science.
If non-scientists believed the scientific consensus the world would be so much better. Now we have
- politicians believing AIDS is not caused by HIV
- celebrities promoting Scientology and the idea that vaccinations cause autism
- medical treatments based on argument and rhetoric rather than evidence
This world needs help, people. Be a scientist. And if you can't, then please believe us and go about your business.
What about critical thinking? Of course I'm in favor of critical thinking. However a little knowledge is a dangerous thing when it comes to scientific claims. Let's take the moon effect as an example.
The idea of the moon effect is that when there's a full moon, people behave more strangely. Nurses and police will often swear that the effect is real. It's not. Study after study has shown that there is no moon effect. Why do people continue to believe it?
First, they use their critical thinking. The argument is that the moon effects the tides, the tides are made of water, and we are 99% water. This sounds very plausible to people. And all of that is true. The problem with it is we have no reason to think that the gravitational pull of the moon will cause crazy behavior. Also, the moon pulls on everything made of matter. There's nothing special about water except that it's liquid and abundant. Also, a nearby building will have more of a gravitational pull on you than the moon, so how come there's no building effect?
Second, there's a little thing called confirmation bias. Once you hear the idea of the moon effect, you start noticing when there is a full moon and people act crazy. We don't think of the moon effect when there's a full moon and nothing special happens, and we don't notice when people act crazy and there's no full moon. Consequently, we build up all these experiences associated with the idea of the moon effect, and we believe it.
You can see how at one level of critical thinking the moon effect is very plausible. The gravity argument has some kind of persuasive sense, and the confirmation bias makes our own experience seem to support the effect.
This is where you need a good understanding of science to know where the flaws are. And many scientists outside of psych and cogsci don't even know about confirmation bias. It takes careful study to find out that the moon effect does not exist. You can't tell if it exists or not based on your own personal experience. You just can't. Finding out if the moon effect exists requires careful, systematic observation. And statistics. If you don't understand that stuff, then please, please, just take my word for it: there is no moon effect.
And when you hear that the scientific community agrees on something, believe whatever it is they say. Otherwise you're just playing yourself.
When scientists have significant disagreement, you're free to believe anything you like. It's still up for grabs. This post only applies to findings that are generally accepted. That is, one or two holdouts don't make something contentious.