I know that if one wants to become a Muslim, then he has to recite syahada to become one. But, what does it mean to recite syahada? "I bear witness that there is no God but Allah" "I bear witness that Muhammad is the Messenger of Allah" Let's underline the word "witness" here. In order for someone to witness, they have to; present in the event, see/hear with their own perception, and believe that it's real. A Muslim witness the oneness of God and the existence of a messenger after they have seen the miracle, which I believe it to be the only way someone can attain faith. What happens next? Does a mualaf already totally sure of God's existence? I mean, he will face fundamental questions as he starts his journey to learn about this religion. As far as I know, Islam does allow Muslims to have some degree of skepticism. In fact, it's presented from a mouth of the angels! (see Q.S 2:30) But then, wouldn't it break a Muslim's testification that he already said to enter this religion? Wouldn't it mean that he hasn't actually believe? Wouldn't it take away the value of syahada in his salah? At the same time, I don't see a way someone can truly acquire faith fully and never have any question left after he enters a religion. It's practically impossible to attain at an early age and also impossible to maintain such purity after the testification. It would also break a statement from Prophet Muhammad which says that faith of a person can fluctuate. So, at what point a Muslim left his religion after questioning his faith? I don't think a Muslim-born person can really acquire faith without being a skeptic at some point of his journey.