REVELATION:
MUSLIM AND CHRISTIAN POSITIONS COMPAREDThe Islamic position
Muslims, like Christians, believe that God speaks to men. Muslims believe that his final revelation was the Qur'ān, a book that God dictated through the angel Gabriel (whom they also call "the Holy Spirit") to Muḥammad (who, they say, is in no way the author), which he in turn preached to the people. The Qur'ān is emphatic in its claim that Muḥammad is the mouthpiece of God whom all must accept. The Qur'ān also speaks often of other spokesmen of God in the past, prophets whose message Muḥammad came to confirm and complete.
Muslim literature presents Muḥammad as the end of a series of prophets (the "seal of the prophets" —Q. 33:40, originally likely to have meant "confirming previous prophets"). Each of these (including Jesus) is said to have preached the same basic Islamic message, but their followers later abandoned their preaching, and true religion died out. Only with Muḥammad was the true religion restored (not founded), which must endure to the end of time. Therefore no other prophet is to be expected.
Islam is said to supersede Christianity, just as Christianity is said to have superseded Judaism. These two religions, moreover, although they still have followers, are false to their founders. The Bible, originally from God, was tampered with and does not contain the real teaching of Jesus or the prophets. So Muslims generally consider the Bible authentic and revealed only to the extent that it agrees with the Qur'ān.
Besides the Qur'ān, Muslims follow Ḥadīth, traditions written down a few hundred years after Muḥammad's death, claiming to represent what Muḥammad said or did. Because Muslims generally believe that Muḥammad was a perfect man who could not sin or make a mistake, his example is held as the model for all mankind. Through him, God teaches people how to behave. So Muslims generally view Ḥadīth as another form of revelation. Yet they do dispute about the authenticity of particular ḥadīths.
The laws contained in the Qur'ān and Ḥadīth constitute Sharī`a. Sharī`a is honoured as divine law, perfect and good for all times sand all places. It is the ultimate authority in Islam. No development of it is necessary or possible. Sharī`a is simply to be applied. New circumstances may come along which require new answers. Muslims may give different opinions, but if they largely agree on one answer, they have "consensus" (إجماع), and that is considered binding.
In an ideal Islamic state no law is accepted but Sharī`a. To place human laws alongside or in place of divine laws is regarded as derogating from God's authority and a violation of the worship of the one God who alone should be obeyed.
While respecting God's sovereignty, Muslims also resort to a vast literature of legal works. These constitute fiqh, and are a human attempt to understand and codify Sharī`a.
Muslims frequently sharply differ on Qur'ān interpretation, the authenticity of particular ḥadīths, and legal positions. Some are slavishly traditional, others are very liberal. Whereas Shī`ites follow the representative of the "hidden imām", Sunnī Muslims recognize no human authority (or magisterium) to decide what is Islamic and what is not. Private interpretation is the rule.
The Catholic position
Catholics believe that God speaks to us in many ways. He speaks through the created world about us and through our natural reason (Rom 1:19-20). He also spoke through the prophets and other writers of the Old Testament. Finally he spoke to us through his Son (Hebrews 1:2).
God spoke through Jesus in his earthly life, by all his words and deeds. But how does Jesus, the eternal Word of God, address himself to us now and at all times, all over the world? Jesus promised that when his earthly life was finished he would give his Spirit (John 14:15-20, 25-26; 16:7-15). The Spirit is the New Law (Rom 8:2), written on our hearts (Jer 31:33) and given through our faith in Jesus. The Church is the continuing visible presence of Jesus in the world, the Body of Christ, while the Spirit is its soul. Fundamentally, the Spirit (and not the Bible) is the supreme authority for Christians.
The Holy Spirit guides the Church in love (John 13:31-35), unity (John 17:21-23) and joy (John 16:20-22). It guided the Church in apostolic times to write its witness to Jesus in the books of the New Testament.
The New Testament (and the Old) is the work of the Spirit together with the inspired human author. God (all three persons as one) is the principal author, while the human author is his instrument, writing under the spirit's guidance. How do we know that a book is inspired and part of the Bible (There are many other "apocryphal" books)? —Not because it is "inspiring", but because the Church, by the authority and guidance of the Spirit, recognizes it as such.
The New Testament teaches us what to believe and what to do in order to receive the power of the Spirit, and shows how to use this gift in a good life. The Bible is a book of past times and does not envisage all the circumstances of life today, but the Spirit continues to guide the Church to understand and apply the Bible wisely. Every Christian, both by the gift of the Spirit and by the exercise of his brains in serious study, can come to understand God's teaching more and more deeply. The Spirit, moreover, distributing his gifts differently, gives to the Pope and the Bishops a special gift of discernment so that they can teach authoritatively what is and what is not Catholic belief, and thus maintain the unity of faith among believers.
The Church makes some laws for the orderly functioning of its organization, but does not pretend to regulate every aspect of a Christian's life. The commandment of love covers everything, but universal laws cannot tell us how we must love in every circumstance. That is left to our conscience, enlightened by accurate information, good sense, good advice, and the inspiration of the Holy Spirit.
This Christian freedom of the Gospel contrasts with the conservative Muslim idea of Sharī`a, which attempts to regulate the whole of life, drawn up in the context of 7th century Arabia, which cannot be altered or adapted to new circumstances.
The Holy Spirit, given to us as the New Law of the gospel, is the most perfect gift of God and the immediate stepping stone to the next life of glory. No other revelation can be expected, since the Son, manifested in his historical life and in the spirit (1 John 5:6-9), is the perfect revelation of the Father and there can be no other.
Therefore, Christians do not accept the common Muslim claim that the Paraclete foretold by Jesus is Muḥammad, or that Islam replaces Christianity as a final revelation. "If we, or an angel from heaven, should preach to you a gospel that is different from the one we preached to you, may he be condemned" (Gal 1:8).