To start, the definition I'm using for "rational" is:
relating to, based on, or agreeable to reason
So, to be irrational is to lack in that. Simply put, it is to be disagreeable to reason.
In my view, religion is irrational. It is a codified belief in unprovable concepts without evidence. I often talk to religious people of various sects. In my experience, religion encourages exactly the wrong way to approach reality.
I see this, for example, in claims of miracles. My default position is skepticism when faced with a claim of supernatural intervention. I am constantly taken to task for not assuming the truth of a miracle claim when that claim has not been substantiated. But I will not budge on this issue. I have some rules of thumb that I start with when evaluating supernatural claims.
- I do not start with belief and work to evidence. It has to be the other way around.
- I do not accept authority or antiquity as reasons for believing.
- If an event is explicable in natural terms, I am not going to ascribe supernatural causes to it.
- To prevent bias(emotional, personal or otherwise), an anecdote must be corraborated with empirical evidence sufficient to make a determination about the nature of the event.
- More generally, any event or item claimed as a miracle has to be open to skeptical investigation, or it is useless as evidence.
1. I do not start with belief and work to evidence. It has to be the other way around.
This means that I am not going to assume that a supernatural claim is true and then attempt to find evidence to support it. For example, the Shroud of Turin is often claimed as an example of a measurable miracle. The only radiological dating we have puts the date of the cloth's creation in roughly the 13 to 14th centuries. There have been calls for more in depth testing, all of which have been turned down by the Vatican. At best, the evidence points away from authenticity. At worst, it is simply too muddled as of yet to make a definitive statement about authenticity. And, so, I am not going to assume that this object is miraculous. This is aside from the fact that there is no evidence of supernatural composition, meaning that even if the cloth did date from the correct time period, it still doesn't constitute proof of a miracle.
2. I do not accept authority or antiquity as reasons for believing.
This is, for the most part, self explanatory. A religious group, making religious claims about an object, is the last group you should trust in regards to authenticity. They have a vested interest in maintaining the belief, and if their claims cannot be substantiated by an independent party, there is no reason to hold belief. So, noting that the Orthodox church holds that the "Holy Fire" event to be miraculous is useless.
3. If an event is explicable in natural terms, I am not going to ascribe supernatural causes to it.
This holds true for the Shroud of Turin, for example. Even if the cloth dates from the correct era, it will only constitute proof of a miracle if the image is proven to be impossible to generate from natural causes. As many people have made convincing duplicates of the Shroud using ancient techniques, it is no simple task to prove such a thing.
This also covers things like "miraculous" cures by faith healers. Unless the healing is impossible from a biological point of view(instant limb regeneration, for example), or that it is part of a testable pattern beyond statistical explanation(a priest who can cure cancers with a touch, for example), then it's useless as proof.
4. To prevent bias(emotional, personal or otherwise), an anecdote must be corraborated with empirical evidence sufficient to make a determination about the nature of the event.
An anecdote is not sufficient evidence, in and of itself, to determine anything. It has to be accompanied by some sort of empirical evidence verifying the claim.
5. More generally, any event or item claimed as a miracle has to be open to skeptical investigation, or it is useless as evidence.
This has to do with miracle claims like the Shroud of Turin and the Orthodox claims about "Holy Fire." In both cases, the church is denying independent investigators access to the relevant information. The Catholic church denies requests for further dating(and, indeed, a recent "restoration" of the cloth may have eliminated the possibility of such dating ever again). The Orthodox church refuses to allow scientific examination of the circumstances surrounding the annual "Holy Fire" event which is claimed to be a miracle.