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There is a very strongly entrenched view among majority of Westerners today that the three main monotheistic religions Judaism, Christianity and Islam share one common God and therefore despite the obvious differences, the core foundation of these three religions is the same. 

 Throughout several centuries many millions o Christians converted to Islam believing just that.

Oppressed by the tax (Jizya) imposed on all non-Muslims living under Islamic law (dhimmis) since the end of the 7th Century AD, they probably thought that changing their religion without changing their god wasn't a bad solution.

The rewards were immediate - a life that was better, free of humiliation and social status equal to other Muslims. Today the common belief among the vast majority of non-Muslims is similar as they think that Allah and Yahweh are the same deities and The Quran is just like the Bible with yet another "New, Islamic Testament" added to it.

In fact the Muslim activists, who try to harvest new converts from among discontented Westerners, propagate this aspect of Islam - the same God with much stricter rules and therefore a purer and truly pious life. They can sow the seeds of their faith on very fertile soil here since clear rules and purity of faith are something that many people need and desire. A religion where they are not forced to compromise their faith in god with new age witchcraft, same sex marriages, moral relativism, self indulgence (sorry, self-discovery) and other "progressive" ideas penetrating some Western Christian churches nowadays.

They are promised they will be given a new burst of faith as soon as they submit to Allah under Islam - the only true religion. They are told that Mary and her son Jesus are "recognized" under Islam and that Islam in fact is the purest form of their "old" monotheistic religion, free from all the errors implanted there by confused Jews and Christians.

The truth about the common origin of Judaism, Christianity and Islam is much more complicated and in fact, speaking strictly from a religious point of view, Muslim Allah and the Judeo-Christian Yahweh come from different worlds and are alien to each other. They are entirely different deities.

Of course all so called Muslim "scholars" will deny this with vigour and bring up evidence against it. Let us look first then why many theologians (apart from some Islamic apologists) reject Allah as the same deity as Yahweh.

A long time before the times of Muhammad the Quraish tribesmen from Mecca (Mohammed's tribe) worshipped well over 360 different deities from which the most powerful was Hubal - the Moon God. It is often argued that the Bedouins (nomads) from the pre-Islamic era were more likely to worship the spirits of their ancestors rather those gods attached to any particular place. And so the moon-god was worshipped initially among the Arabian Peninsula city dwellers.

       Why  the Moon God?

The evidence points to the ancient beliefs of the Middle East. The Arabs who settled in the cities inherited the Moon God from the civilizations of Mesopotamia. Ancient Sumerians worshipped the Moon God under several names and among them were Nanna, Suen and Asimbabbar. The symbol of the Moon God  was the crescent moon.
 

Photograph from (Allah - the Moon God )

Later, the Sumerian Moon God was adopted by the Semitic people of the Ancient Middle East. The Assyrians, Babylonians, and the Akkadians took the word Suen and transformed it into the word Sin as their favorite name for the Moon-god.

Photos from (Archaeological photo gallery of the Arabian Moon-God 2000-900BC )

As Prof. Potts pointed out, “Sin is a name essentially Sumerian in origin which had been borrowed by the Semites.” In ancient Syria and Canna, the Moon-god Sin was usually represented by the moon in its crescent phase. (Full Article)

The Symbol, the crescent moon, is very important here because Muslim scholars argue that the presence of the Moon God in Arabia proves nothing. Sure - they say, there was Hubal in Mecca and this deity was worshipped there together with other 360+ gods. This is why Muhammad got rid of all these idols and converted all the Arab tribes into the only and true religion - Islam.

There are however strong arguments against this interpretation.

If it is true that Muhammad abandoned all ancient Quraish deities and Hubal - the most powerful one, why is it that many Islamic rites and customs are the same as the old pagan ones?

In Islam most of the rituals performed (today) by devoted Muslims in the name of Allah are connected to the pagan worship that existed before Islam. Pagans practices of the Pilgrimage of Kabah once a year–the Fast of Ramadan, running around the Kabah seven times, kissing the black stone, shaving the head, animal sacrifices, running up and down two hills, throwing stones at the devil, snorting water in and out the nose, praying several times a day toward Mecca, giving alms, Friday prayers, etc. are strictly followed by Muslims today. Nobody can deny the fact that, all the above rituals of Muslim’s hajj today—existed well before the arrival of Islam. (source )

The word "Allah" was used to describe Hubal long before Muhammad as well. For those who want to follow up the etymological discussion concerning these words, several arguments can be found very well summarized by Syed Kamran Mirza  HERE 

The presence of the crescent and the star, as symbols of Islam, makes a lot of Muslims very uneasy these days. It is the the possibility that other people may believe Allah to be an ancient pagan god instead of the god of Abraham and Moses, which worries them. And so they argue the Crescent and the Star are not actually Islamic. It was the Turks who adopted it from .Constantinople. They claim further - the Crescent and the Star had not been used by the Muslims before the fall of Constantinople (1453).

The star and the crescent as depicted in a few flags of Muslim countries do not have any significance in the Islamic faith. In other words, the reason for depicting these symbols on flags is not Islamic or religious. On the contrary, it is primarily a continuation of a tradition set by the vast Ottoman-empire (for a period of over half a millennium), which has prompted some of the modern Muslim states to depict these two symbols on their flags. One may, however, ask why did the Ottoman-empire opt for the star and the crescent on its flags. No specific answer can be given for this question. There could be a number of possible reasons.(Source)

Furthermore, the Muslims experts will argue, it was Muhammad himself who had the revelations from Allah, and who told him all about Ishmael, Abraham, Moses and Jesus and so we know from the main source that Muhammad was considered the most important and the last prophet.

Well this still leaves one additional problem. Why is it that the insignificant sign of the Crescent can be seen on all mosques, prominently displayed on their  minarets and domes?

Let's us consider the validity of some  Islamic arguments.

Unlike the Old or New Testaments, the Quran isn't a narrative. It consists mostly instructions and rules mixed with references to the book and a lot of repetitive material. The sparse and contradictory references to biblical stories indicate that Muhammad did not have the slightest idea what Judaism or Christianity were all about. He understood religion to blind obedience and repetitive rites and rituals rewarded by simple pleasures (on earth and in paradise): booty, gold, horses, camels, comfort of the tent and lots of sex. You can review most of the biblical errors and contradictions which the Quran contains HERE .

Muhammad learnt soon enough that his knowledge of the Bible was not up to the task to convince the Jews and Christians that he was one of the Lord's prophets and so he accused them of changing the true story. In fact he 'made' all  ancient prophets from the past  testify  against all Judeo-Christian beliefs. This was a clever ruse.  From then on he did not have to learn much at all and he just used his imagination in creating a "biblical" past which overrode the existing tradition.

Why did Muhammad try to absorb Judeo-Christian beliefs in Islam?

Rejected by his own tribesmen as a prophet, Mohamed had to consider the Jews and Christians living on the peninsula as his next targets for conversion. From his point of view there was not a great deal of a difference - one god is one god- and so after "experiencing" some "extra revelations" Mohamed included ALL people of the book or scripture as acceptable followers.

After his "escape" to Medina, Muhammad, found there a rich and vibrant Jewish community and so he tried to convince those people to become his followers. At this stage he even forced his companions to pray in the same direction as the local Jews and to fast at the same time.

The Jews of Medina rejected Mohammed's conversion proposals. His second hand knowledge of the Jewish Holy Scriptures and his inability to grasp the irreconcilable differences between his Koran and the Jewish religion made it impossible for him to argue his case and win the Jewish support. Mohammed's initially favourable opinion about the Jews turned into anger and so he reverted to facing Mecca in his prayers and to Ramadan as the fasting period.

Let us return to consider the Crescent being adopted from Constantinople by the Turks. Well I am afraid it is just another piece of Muslim deception.

Unfortunately for the Muslim theologians and apologists there is massive evidence, which clearly proves that The Crescent and the Star were used widely in diffrent parts of the Islamic empire, long before the fall of Constantinople.

The Crescent and the Star symbol was used very frequently on Muslim coins for example.

Late 7th Century AD Silver Arab coin form Iraq (original ) or similar

The Hubal insignias were also used In jewelry:

Pendant, 11th century; Fatimid Egypt (source )

Pair of earrings, 11th century Greater Syria Gold: fabricated from wire and sheet, decorated with granulation; originally outlined with strung pearls and/or stones; 1 x 1 1/4 in. (2.5 x 3.3 cm) Purchase, Gifts in memory of Richard Ettinghausen, and Harris Brisbane Dick Fund, 1979 (1979.278.2a,b) 

An elaborate example of filigree and granulation work from the Fatimid period in Egypt and Greater Syria (969–1171), this pair of earrings is illustrative both of the most characteristic goldsmith work and of one of the most popular shapes for jewelry of this period—the hilal, or crescent (moon). The basic vocabulary—a box construction, rings for stringing pearls or semiprecious stones, openwork S-curves, arabesque designs, and the crescent shape itself—seems to have dominated jewelry production in the Fatimid world into the second half of the eleventh century and perhaps later. The influence of this vogue was widespread. Goldsmiths working under the Mamluks (1250–1517) adapted this vocabulary, as did jewelers of Nasrid Spain (1232–1492), while echoes reverberated into Kievan Russia, Ottoman Turkey, Mughal India, and North Africa. (SOURCE )

Armaments also  used to bear the  Crescent and the Star

Persian armor of the 10th - 12th century, museum display in Iran. (source)

Then, there are also paintings and drawings  depicting Islamic Mosques from areas, which then were not covered by the Ottoman Empire and from the times before the fall of Constantinople.

 Page from a manuscript of the Laila and Majnun of Nizami, dated 1432; Timurid Afghanistan (Herat)

Laila and Majnun at School: Page from a manuscript of the Laila and Majnun of Nizami, dated 1432; Timurid Afghanistan (Herat) Ink, colors, and gold on paper; H. 12 3/8 in. (31.3 cm), W. 9 in. (22.9 cm) Purchase, Lila Acheson Wallace Gift, 1994 (1994.232) This splendid copy of the story of Laila and Majnun by the twelfth-century Persian poet Nizami was commissioned by one of the most discerning of patrons, the Timurid prince Baisunghur. The colophon states that it was made in Herat (the Timurid capital, now in Afghanistan) in A.H. 835 (1432 A.D.) and copied by Jacfar, a celebrated calligrapher in charge of the royal atelier. The manuscript contains one magnificent miniature (two others are in a private collection and one is missing) of Laila and Majnun at School. The painting, which spreads from the usual confines of the text into the margin, shows a domed building with a minaret—a madrasa, or religious school, where the star-crossed lovers, children of Arab tribal chiefs, first meet. The salmon-colored bricks and the intricate decoration reflect both the illuminated opening pages of the manuscript and the brick and tile work of eastern Iranian buildings. The schoolroom floor is covered with an unusual multiple-niche prayer rug (sajada). The girls and boys are separated, except for Laila and Majnun, who sit at the back. The teacher listens to a pupil in the center of the room, while a latecomer tries to slip in unnoticed. (SOURCE )

Incense burner, 11th century Spain (Andalusia) 

Incense burner, 11th century Spain (Andalusia) Cast bronze, openwork and incised; (a) Gr. H. 4 7/8 in. (12.4 cm), Max. L. 10 1/4 in. (26 cm), Max. Diam. 4 in. (10.2 cm) Louis V. Bell Fund and Joseph Pulitzer Bequest, 1967 (67.178.3a,b) The square shape, high domed lid, long horizontal handle, four zoomorphic feet, and openwork horseshoe arches on the lower register of this incense burner identify a specific typology that fits well into a western Islamic, almost certainly Spanish production. The crescent finials and the projecting winged section atop the vault of the lid enliven the otherwise compact and severe form of this object. (SOURCE )

There was the crescent symbolizing Hubal and the Star as his prophet long time before the fall of Constantinople and the heroic death of the last Byzantine emperor who was killed defending the walls of what was left of the Eastern Christian Byzantine Empire.

And so the Crescent and the Star do symbolize not only the ancient Moon God and his prophet but also the link with the ancient polytheistic world of beliefs (some theologians argue that the star - initially a female deity, symbolizes not Mahomet but Islam).

This is also why we have certain problems in understanding the mentality of Muslims.

For the ancient world it was important to keep the gods happy and it was irrelevant how many atrocities were committed in due process. Lying was only bad when it displeased the gods, stealing and looting for your gods was fully justified. And so it is for the Muslims, who must submit to their god and all good deeds are not there for their own sake but to make him happy.

The Judeo-Christian tradition created objective ethical values - good and evil. These values exist independently of our own existence as opposed to the values of the ancient gods where GOOD was what the Gods liked even if it was killing other human beings or pillage or destruction.

On occasions like this many would point out that Christians are perfectly capable of killing as much as Muslims.

Of course this is true.

Ancient pagan religions justified our weakness, cruelty, greed: in contrast the new religion did not justify our weakness but tried to enable us to rise above it - the new religions Judaism and later on Christianity, tried to improve human kind and were the basis for much of the scientific, social and artistic development in the western world.

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