As Islam constantly invites non-Muslims to enter its fold, every non-Muslim who accepts that invitation necessarily repudiates his original doctrine to the extent to which it is inconsistent with Islam and wholeheartedly subscribes to Islam. Thus he becomes an apostate in the eyes of his original co-religionists. If the penalty of apostacy from Islam is death, would it be unreasonable for other faiths also to impose the penalty of death for apostacy from those faiths? This would mean that no change of faith would be permissible under any circumstances and that everyone must continue to adhere to the doctrines and teachings of the faith into which he may be born. The accident of birth would determine everyone’s belief and freedom of conscience would become a myth.
Also, in such a state of affairs, if a follower of one faith became convinced of the truth of another faith he would be under compulsion to continue to give lip service to the doctrines of the faith into which he was born, though he would have ceased to believe in them. In other words he would be a hypocrite. The Holy Quran condemns hypocrisy in the strongest terms. For instance, it is said: Convey to the hypocrites that for them there is a painful torment (4:139); and again: The hypocrites shall surely be in the lowest region of the fire, and thou shalt not find that they have any helper (4:146).
Again, it is pointed out that if force or pressure had been permissible in matters of faith God Almighty, Who can force a person to believe, would have compelled the whole of mankind to become believers, but He leaves everyone the choice to believe or to disbelieve. How can it, therefore, be permissible for any human being to exercise compulsion in matters of conscience when any compulsion exercised by a human being cannot even be effective? For instance, it is said: If thy Lord had enforced His will surely all those on the earth would have believed, without exception, wilt thou, then, take it upon thyself to force people to become believers? Except by Allah’s leave no one can believe; and He will afflict with His wrath those who will not use their understanding (10:100-101).
One Muslim divine, who has a considerable following, has coined the cliche that the door of Islam opens only inwards and does not open outwards, and that, therefore, whoever attempts to emerge from Islam forfeits his life. It is a stupid utterance which has neither rhyme nor reason to support it.