A teacher of mine was a born Christian. He searched for a true religion, and after reading about Islam, he found it to his liking and embraced it. Then, after a while, he reverted. Something similar happened to someone else I know but instead of finding Islam appealing, it didn’t make much sense to him, and so he didn’t become a Muslim. Both people searched for the truth, but I guess only God can judge how much in their hearts they really wanted to be guided. What about the reverted and what will happen to the latter in question? He searched, did his best, didn’t accept Islam on grounds that must have made sense to him and remained a disbeliever. Is he at fault?
The general principle which the Qur’an mentions in this regard is that Allah Almighty will make people accountable on the basis of their circumstances and abilities. If someone couldn’t get the opportunity to know the truth in its final form yet he continued to search for it, most certainly he will not be punished for not being able to find it. He is going to be rewarded for the good effort he had undertaken. If, however, on the other hand, it is established beyond doubt that the person knew what the truth was but for one petty reason or the other he declined to accept it then he’ll be punished for rejecting God’s message. Any particular case is of that person who failed to see the truth in the message is something only Allah Almighty, with His unlimited knowledge, can decide. This is exactly what He will do on the day of judgement.Courtesy: http://www.islamicissues.info/qa_question.php?qid=130