Religion is irrational
Theists are often called irrational by their critics because of their tendency to: 
- disregard for any evidence, either reliable supporting evidence or evidence contrary to their position,
- claim something is an explanation even though it does not actually have any explanatory power,
- accepting one set of beliefs but rejecting other equally valid beliefs,
- express certainty where it is not justified,
- rely on fallacious reasoning, such as the argument from ignorance,
- not guard against human biases and accept beliefs simply because they are comforting,
- acceptance of synthetic or absurd a priori beliefs.
Apologetic arguments are credible
Many apologists rely on arguments that they consider to be valid and sound. Skeptics often disagree with this position.
It is an answer to transcendental questions
God is sometimes adopted as an explanation that addresses transcendental questions like: why are we here?
- "[Science]cannot tell us why we are here (although it may have some very interesting insights in how that happened). When it comes to questions of meaning, purpose and value, science is blind [...] To use the language of philosophy, God is the “best explanation” of the way things are. We can’t prove that God is there, any more than an atheist can prove that there is no God. But all of us, whether Christians or atheists, base our lives on at least some fundamental beliefs that we know we cannot prove. That’s just the way things are."
- "The confusion here comes from supposing that whatever is not rational must be irrational and forgetting that there is a huge area of life where questions of rationality are wholly irrelevant."
Of course, this assumes a particular religion is the answer. It also assumes that these questions have an answer at all! On the other hand, any system of thought that addresses transcendental questions is likely to have a "non-rational" component.
- "If anything does replace a religion, it will in fact be something that does the same job – which, as far as I am concerned, makes it another religion."
Reason does not apply
It is obvious that most decisions humans make are not rational but rather instinctual or habitual:
- "Humans do not really lead rational lives. Many of our everyday thoughts, decisions and activities have little to do with rationality. Indeed, the real surprise is that we manage to think and act rationally as much as we do."
More controversially Theists may argue that religion is another way of knowing:
- "Christianity claims there are truths which are beyond the power of reason to demonstrate, but that doesn't mean it's irrational. There's a difference between what is irrational (against reason) and what is suprarational (above reason). [...God] has revealed things which are beyond reason, but which don't conflict with it."
Strong atheism is irrational
When the issue of the irrationality of theism is discussed, apologists often point out that the belief in the "non-existence of God", know as strong atheism, is also (arguably) irrational. However, this is a red herring since it does not relate to the rationality of religion.
- "In this day and age most scientists are religious. [...] 80% of the world population have strong religious beliefs."
Cross cultural occurrence
- "[...] there was no way for such an idea to have spread so rapidly and consistently throughout the world!"
- Religious belief is harmful to the individual
- Religion is harmful to society
- Religious belief is beneficial to society