I submit that there can't be a logical defense. This is not because of a weakness in religion but rather because of a weakness in logic. To get to the point where logic becomes relevant you have to build up a set of shared assumptions. The beliefs from which you argue are formed from a set of experiences. Unless you have something of a common experience it is difficult to share a set of beliefs from which to argue. The process of joining a religion is not a logical one. It is a spiritual one and is based in experience.
How, then, do we argue about experience? Either we discuss things and times and places that neither of us have witnessed, or we discuss and evaluate each others experiences. Perhaps we are fortunate and both accept a common ground distilled from some set of experiences. Maybe we are both physicists. But no such set of shared experiences seems to be broad enough to properly answer questions of religion.
If you truly want to begin to discuss intelligently then you have to seek a shared set of religious experiences. But that might be dangerous. Change can happen at that point.
I don't understand how shared assumptions being the basis of logical argument constitutes a flaw. Could you explain this further?
We argue about experiences in science all the time. We do this by documenting steps regarding how we rendered our experience so that other people may also experience what we did and perform measurements and comparisons and analyzations, et cetera, and once we've done that, we can apply other intellectual tools we have, like logic.
How do I render a religious experience for myself?
Thanks for replying to my comment. I was a bit surprised that no one did for a little while.
Although I said "weakness in logic," I didn't mean to say that logic is weak or flawed. I really meant that it is insufficient to use logic in the absence of shared assumptions. As you point out, sharing of assumptions can come through communicated and shared experiences.
I think that your description of how learning comes about in science is a powerful one. I believe that some aspects of it should apply to religion.
In my particular religion, the process of gaining faith, and then of moving from faith to knowledge is framed almost as a science experiment. You apply particular principles and see what the outcomes are. As you see the outcomes your faith grows. (See Alma 32:26-36 in the Book of Mormon--available online through LDS.org.) Faith is a word for something less than knowledge that becomes knowledge only through experience. You might look at it from a Bayesian perspective and say that with more data uncertainty grows smaller.
"How do I render a religious experience for myself?" This question strikes me as a little bit odd, and that may be because of a weakness in the metaphor between science and religion. Science studies things. Religion studies the Divine. What I mean is that religious experience may be more of a conversation than a solitary experience. Conversations happen by mutual agreement. However, it is still a good question because it shows progress from worrying about a tool that processes information to worrying about how to seek new information.
Here is a simple religious experiment: pray to God and ask if He can hear you. Document your frame of mind when you prayed. Did you actually want an answer? Were you willing to accept the possibility of no answer? Document any answer or lack of answer you experience.
In science, we generally come to knowledge only slowly, over time--although sometimes things progress more quickly than other times. It is the same in religion. The most likely answer to such a prayer is a gradual one, something spoken quietly to the heart. Such an answer is partial, at best. Maybe you manufactured it mentally. Maybe you didn't even hear anything. It was so quiet. Was anything really there? But something was there. At least enough to follow up on. And you move forward from there, performing experiments, seeking answers, asking questions and listening and acting. Just like a signal, over time, can appear out of noise, so religious truth, over time, arises out of uncertainty. You talk with others and compare notes. But in the end, for something this important, you really want to know for yourself. You have to perform the experiments, you have to have the experiences, you have to gain the knowledge for yourself. Besides, it's not like physics. With religion, everybody seems to be saying different things than everybody else. So it becomes up to you.
LDS missionaries seek to guide one person at a time through experiences that lead to enough personal knowledge of the gospel to warrant baptism. As far as I know, this is the only way that they can be effective.
How, then, do we argue about experience? Either we discuss things and times and places that neither of us have witnessed, or we discuss and evaluate each others experiences. Perhaps we are fortunate and both accept a common ground distilled from some set of experiences. Maybe we are both physicists. But no such set of shared experiences seems to be broad enough to properly answer questions of religion.
If you truly want to begin to discuss intelligently then you have to seek a shared set of religious experiences. But that might be dangerous. Change can happen at that point.