What I'm about to say applies to many, though not all, Muslims. Disclaimer done.
Having left Islam for Christianity, I constantly receive emails from Muslims urging me to return to Islam. I appreciate the concern that these Muslim friends are displaying for my soul, but I do see a very prominent and recurring theme in these emails. They usually state something along these lines:
"How could you leave the truth for Christianity?!"
"Astaghfar -- how did you, a Muslim boy trained in Islam, leave it for falsehood?"
Now, the people who write these emails are usually responding to my testimony (here) which is full of the reasons why I left Islam. But still, when they email me, they ask me how I could have left Islam for falsehood, as if Christianity were ipso facto false.
Do not be misled - their question is very straightforward and telling: "How could you leave the truth for falsehood?" If this were a statement of disagreement with my conclusions about Islam and Christianity, they'd say so: "How could you believe that Jesus rose from the dead?" or "How can you subscribe to the idea that God would die for our sins?" However, this is not what is asked - such arguments are generally ignored wholesale. Rather, they simply assert that I left the truth for falsehood, insinuating that I left Islam without contemplating the issue of its truth, as if I were blindly attracted to Christian claims and doctrine.
What is often ignored, though, is that I arrived at the conclusion that the truth claims of Islam are not as grounded in evidence as are the truth claims of Christianity. That's why I became a Christian. Even after reading my entire testimony, Muslims will often fail to consider even the possibility that Christianity is true and Islam is false. It's as if, to the Muslim, Christianity can be nothing but falsehood and Islam can be nothing but the truth.
I think it's obvious, but for the record: if we are discussing whether Islam or Christianity is the truth, asking me how I could leave the truth for falsehood is begging the question.
The purpose of this post, though, is not to rant. It's to point out the deep-seated presupposition most Muslims have when studying Islam and Christianity: that Islam is true and that Christianity is false. To the average Muslim, this is not a conclusion but a given. To the average Muslim, then, Islamic apologetics is an exercise of proving a given, something as established as the laws of mathematics, and frustrations mount when someone else starts claiming that 2+2 does not equal 4 after all.
I know because I was there.
To the Christian, let me assure you: there is a breaking point. At some point, your Muslim friend will realize that this very fundamental given is causing him to reinterpret every piece of evidence laid before him. Until that point, his denials will mount and his defiance will grow. You will probably only succeed in making him more Muslim. But when that breaking point is reached and he realizes that his given might not be a given after all, you will see a man who will be faced with the option of truly accepting God. If he does, it will be a beautiful thing, because it will cost him everything: his support, his family, possibly even his job or his life. But this is beautiful because his purpose in life will be serving the Truth.
To the Muslim who may be reading this, humor me for a moment. Can Jesus be God? Your answer is most likely "Surely not!" But note that your response presupposes something: that Islam is true. That God would never become a man is an Islamic idea - taking a simple theistic viewpoint, there is no problem with a divine incarnation whatsoever.
What about the Trinity? Is it possible that God can be three-in-one? Your answer: "That doesn't make any sense - in order to have one God, God must be completely and absolutely indivisible!" But note that your response presupposes something: that Islam's view of monotheism is true. That God cannot be a trinity is an Islamic idea - taking a simple theistic viewpoint, there is no problem if God has revealed that He is more incomprehensible than any other thing we know. If God says He is one, but that there is diversity in His unity, then there's nothing inherently wrong with that unless you already assume Islam is true.
Let us continue with our investigation of the truth, the Muslim on his path and the Christian on his. But let us do it with the knowledge of this underlying presupposition that has been ingrained into the very fiber of almost every Muslim. Is Islam the truth? Make sure you have not assumed an answer while investigating this vital question.
**P.S. I understand we all have biases, and Christians are not exempt. We should all work past our biases and none of us entirely can. But what I have tried to point out in this post is that the Muslim bias towards their beliefs often goes far beyond a simple bias and comes a lot closer to circular reasoning, and this phenomenon should not be ignored.**