Imagine a friend has suffered from cancer, and is now told that it is gone. An example of A is to think your friend is free from cancer forever. An example of B is to think that your friend is free from cancer for now. What distinguishes these worldviews? Someone subscribing to A (Person A) hopes the information will lead to a favorable conclusion and, then, for whatever reason, decides to believe it will. Someone subscribing to B (Person B) might hope for the same, but does not decide to believe it.
Logically, Person A's reasoning is:
1. X says that Y attains now.
2. I want Y to attain forever.
3. Therefore, Y attains forever.
Person B's reasoning is identical to Person A's in premises 1 and 2, but it differs in its conclusion as:
3. Therefore, Y attains now (and I must wait to see if it attains forever).
It is easy to see that Person A is behaving irrationally while Person B is not. Yet, it is not always so easy to decide what is rational. Think about the Sun rising each day. Is it rational or irrational to think that the Sun will rise tomorrow because it rose today and yesterday? Strictly speaking, it is irrational. The past cannot assure the future.
Yet, if we actually thought this way, then we would not make many rational decisions. Our motto would be "Induction Good, Deduction Bad." Of course, we might have trouble convincing nonbelievers that induction will continue to be good. The laws of nature, and, consequently, the laws of logic, could change at any moment, so who is to say what is good or bad, or true or false, at a future time?
Rationality is found in probability. The Sun will probably rise tomorrow given its past and present actions. My friend is probably free from cancer forever given the past success of a certain drug and my friend's present state of health. These are rational assumptions only because they are probabilistic. Were they deterministic, assuming what must be instead of what might be, then they would be irrational. There is a world of difference between probabilistic and deterministic assumptions in this regard. The former represents the world of reality and the latter represents the world of fantasy. The former reflects what we know and the latter reflects what we wish we knew.
Now, think about this in terms of religious belief. Religious belief involves belief in the truth of a religious claim(s). Moreover, especially with Western monotheistic religions, religious belief extends to include faith that certain logically implausible or impossible claims are true, which makes this type of faith one that holds despite the evidence. In other words, religious belief is admitted as irrational by those who hold it.
I am not arguing, mind you, that theists are genetically hardwired to be irrational. Theists are no different from atheists with respect to their brains' logical, pattern-matching functionality. The difference between theists and atheists is that theists are willing to accept irrational beliefs and behaviors in one, peculiar area of their lives, namely, that which concerns religion. Why? Why should religious belief, probably the most important kind of belief a person can have, be tolerated if it is irrational? What makes theists buy into it?
It is precisely because religious belief is so important that people want to have it so much and are willing to do anything, even to embrace irrationality, leading to such horrors as war, the destruction of our planet, and, potentially, the destruction of our species. People will do anything for what religious belief offers, which includes immortality, eternity with loved ones, and ecstatic joy. People will do anything for a glimpse of Heaven.
What I have never understood is why so many people are unwilling to give up their dreams when the hard, cold facts of reality affirm that those dreams cannot be real. Our experience of the world tells us that people do not have souls, so why do we believe they do? Our experience of the world tells us that time does not stop, so why do we think it has? Why do people believe so many far-fetched claims? Furthermore, why do they believe them with such supreme confidence when, even if probable, they might not be impossible to disprove? What prevents a person from thinking rationally? What allows a person to embrace irrationality? Is it emotional overload? Is it poor education in reasoning? What separates theists from atheists on these important points? Despite the temptation, I refuse to believe that we are different. After all, theists become atheists and atheists become theists. It seems that something within the human mind switches off and stops working or malfunctions when people choose to believe irrational claims and to believe them decisively. Something is wrong with theists.