The Quran claims to be completely comprehensive in its instructions, being fully detailed:

There is not an animal in the earth, nor a flying creature flying on two wings, but they are peoples like unto you. We have neglected nothing in the Book (of Our decrees). Then unto their Lord they will be gathered. S. 6:38 Pickthall

Shall I seek other than Allah for judge, when He it is Who hath revealed unto you (this) Scripture, fully explained? Those unto whom We gave the Scripture (aforetime) know that it is revealed from thy Lord in truth. So be not thou (O Muhammad) of the waverers. S. 6:114 Pickthall

This is the path of thy Lord, a straight path. We have detailed Our revelations for a people who take heed. S. 6:126 Pickthall

This Quran could not possibly be authored by other than GOD. It confirms all previous messages, and provides a fully detailed scripture. It is infallible, for it comes from the Lord of the universe. S. 10:37 R. Khalifa

In their history verily there is a lesson for men of understanding. It is no invented story but a confirmation of the existing (Scripture) and a detailed explanation of everything, and a guidance and a mercy for folk who believe. S. 12:111 Pickthall

One day We shall raise from all Peoples a witness against them, from amongst themselves: and We shall bring thee as a witness against these (thy people): and We have sent down to thee the Book explaining all things, a Guide, a Mercy, and Glad Tidings to Muslims. S. 16:89 A. Yusuf Ali

Nothing could be further from the truth! The Quran fails to provide many important details in relation to key passages. This in turn leaves the reader confused and even perplexed in trying to understand the Quranic narratives and/or specific injunctions. In the words of the late Iranian Scholar Ali Dashti:

"The Qor'an contains sentences which are incomplete and not fully intelligible without the aid of commentaries; foreign words, unfamiliar Arabic words, and words used with other than the normal meaning; adjectives and verbs inflected without observance of the concords of gender and number; illogically and ungrammatically applied pronouns which sometimes have no referent; and predicates which in rhymed passages are often remote from the subjects. These and other such aberrations in the language have given scope to critics who deny the Qor'an’s eloquence. The problem also occupied the minds of devout Moslems. It forced the commentators to search for explanations and was probably one of the causes of disagreement over readings." (Dashti, Twenty-Three Years: A study of the Prophetic Career of Mohammad, Allen and Unwin, London, 1985, pp. 48-49; underline emphasis ours)

"To sum up, more than one hundred Qor’anic aberrations from the normal rules and structure of Arabic have been noted. Needless to say, the commentators strove to find explanations and justifications of these irregularities. Among them was the great commentator and philologist Mahmud oz-Zamakhshari (467/1075-538/1144), of whom a Moorish author wrote: ‘This grammar-obsessed pedant has committed a shocking error. Our task is not to make the readings conform to Arabic grammar, but to take the whole of the Qor’an as it is and make Arabic grammar conform to the Qor’an.’" (Ibid., p. 50; underline emphasis ours)

An example of such incoherence and unintelligibility is the Quranic view of strong drinks and wine. The Quran is clearly confused regarding its view of intoxicants as the following passages conclusively demonstrate:

And We have not revealed to you the Book except that you may make clear to them that about which they differ, and (as) a guidance and a mercy for a people who believe. And Allah has sent down water from the cloud and therewith given life to the earth after its death; most surely there is a sign in this for a people who would listen. And most surely there is a lesson for you in the cattle; We give you to drink of what is in their bellies -- from betwixt the feces and the blood-- pure milk, easy and agreeable to swallow for those who drink. And of the fruits of the palms and the grapes -- you obtain from them intoxication (sakaran) and goodly provision; most surely there is a sign in this for a people who ponder. And your Lord revealed to the bee saying: Make hives in the mountains and in the trees and in what they build: Then eat of all the fruits and walk in the ways of your Lord submissively. There comes forth from within it a beverage of many colours, in which there is healing for men; most surely there is a sign in this for a people who reflect. S. 16:64-69 Shakir

The impression given by this passage is that intoxicants are something good, since the context deals with signs or proofs of God’s care and provisions for mankind. Nothing is said about the negative affects of intoxicants or whether it is impermissible for believers.

O you who believe! do not go near prayer when you are Intoxicated (sukara) UNTIL YOU KNOW (WELL) WHAT YOU SAY, nor when you are under an obligation to perform a bath -- unless (you are) travelling on the road-- until you have washed yourselves; and if you are sick, or on a journey, or one of you come from the privy or you have touched the women, and you cannot find water, betake yourselves to pure earth, then wipe your faces and your hands; surely Allah is Pardoning, Forgiving. S. 4:43 Shakir

This verse forbids Muslims from coming to prayers while intoxicated. This gives the impression that drinking before praying is permissible, provided that one doesn’t get drunk.

They ask thee concerning wine (al-khamri) and gambling. Say: "In them is great sin, AND SOME PROFIT, for men; but the sin is greater than the profit." They ask thee how much they are to spend; Say: "What is beyond your needs." Thus doth Allah Make clear to you His Signs: In order that ye may consider. S. 2:219 A. Yusuf Ali

Here, wine (which falls under the category of intoxicants) is said to be both sinful and profitable, with the sin being greater. Even this passage stops short of explicitly prohibiting the consumption of wine.

Finally:

O ye who believe! Intoxicants (al-khamru) and gambling, (dedication of) stones, and (divination by) arrows, are AN ABOMINATION,- OF SATAN’S HANDWORK: eschew such (abomination), that ye may prosper. Satan's plan is (but) to excite enmity and hatred between you, with intoxicants (al-khamri) and gambling, and hinder you from the remembrance of Allah, and from prayer: will ye not then abstain? S. 5:90-91 A. Yusuf Ali

This passage says that intoxicants are the handiwork of Satan! Hence, the Quran goes from describing wine as something good to something completely evil.

Now a Muslim may interject here and claim that the verses which permit intoxicants were abrogated. Yet, this is precisely the point. How does a Muslim know that these verses have been abrogated? Where does the Quran explicitly, or even implicitly, state this? Second, how does the Muslim know for certain which verses came first? Does the Quran give the date these "revelations" were allegedly sent down so that we can know which passage came first? After all, one can just as likely claim that S. 16:66-67 was "revealed" last and therefore abrogated S. 2:219 and 5:90-91. How can one know for certain?

A Muslim may claim that Muslims don’t follow the Quran alone, but also consult the hadith literature. If so, then try telling the following Muslims that they need the hadith literature: