Islam is the largest religion in Turkey; sources like CIA World Fact Book state that 99.8% are Muslim, but this is incorrect, 76% is a better estimate. The state is defined as secular, but as the text below show, this is a questionable truth.
Christianity, which has deep roots in Turkey has almost been eradicated, mainly by brutal campaigns in the 20th century.
By its constitution, Turkey is a secular state, meaning that the state is not governed according to religious principles. But the actual image is complex and official statistics on religion, which are nothing but brutal falsifications, are a main indication for what really happens. When all Turks are considered Sunni Muslims, then all funds can be allocated to Sunni institutions and religious education can be fitted Sunni theology. Religious matters are administered through the Presidency of Religious Affairs, but they only accept Sunni mosques, which means that Alevism have no benefit from this, as they do not use mosques and imams, rather cem evi and dedes.
It is not permitted to run private religious schools or universities, no matter what religion.
However, in real life, Turkey is a country of extreme religious discrimination. Practically all funds are allocated to the Sunnis, next to nothing to the Alevis, and the few Christians remaining have faced many problems both with authorities as well as society.
The secular Turkey abolished the caliphate in 1924, nationalized religious foundations and placed heavy restrictions upon religious education. Sufism, a popular and often clandestine form of popular religion, was suppressed.
This policy was eased up in the 1950's, to meet the needs and wishes of a large segment of the population.
More reforms came in the 1970's and 1980's, when leading politicians came to consider religion as a good alternative to communism. This allowed the emergence of a new generation of conservative and religiously motivated politicians. Although Turkey did not fall into the trap of Islamism as seen in other Muslim states, this generation of Islamic politicians have come to dominate the present society.
Most Turks belong to Sunni Islam, with a Shi'i minority in the east. As mentioned, Islam in Turkey is officially all about Sunnism, but realities are somewhat different.
Sunni Islam is controlled and funded by the Presidency of Religious Affairs, which effectively runs and funds 75,000 mosques and their employees, who are considered civil servants.
Religious education is also run by the government, through the Imam Hatip Lisesi which teaches Sunni theology and Sharia. Also here, modern sciences are included in the curriculum is allowed which benefits only Sunni Islamic community in Turkey. This type of high schools teach religious subjects with Western-style science.
Sufism has deep roots in Turkish society, and represents to a large degree a non-Islamic trend of the society, although all Sufis and most non-Sufis will claim that Sufism is very much a part of Islam.
With Sufism comes the veneration of saints and pilgrimages to shrines and graves of Sufi shaykhs.
In modern Turkey, many of these practices have suffered from government initiatives that limits the cults and forbids many traditional practices. Still, the situation for Sufism has largely improved since the middle of the 20th centuries, when many of the groups were effectively closed by the government.
Turkey is home
The fact is that Alevism, which is then made out to be a branch of Shi'i Islam, does not fit necessary definitions to be part Islam. A quarter of the Turkish population are Alevis, and with a modern world view they have been central in securing a secular Turkish state.
Turkey is one of the main regions of early Christianity, it was in Antakya that the term "Christians" was used for the very first time. Many of the earliest Christians figures were born here, such as the Apostle Paul of Tarsus, Timothy, St. Nicholas (Santa Claus) of Myra. For a thousand years, the Hagia Sophia was the largest church in the world. All of the first seven Ecumenical Councils which are recognized by both the Western and Eastern churches were held in what today is Turkey, and the Nicene Creed, which defines many of the fundamentals to Christian theology, is from what today is Iznik.
The few Christians are mainly Armenians who still live in Turkey even after the intensive massacres conducted by the young Turks between 1915 and 1923, where some 1 million Armenians were killed. There are some Shi'is living in the southeastern parts of Turkey, making up some per cent of the population.
Christian communities of Turkey are not allowed to train their own clergy in Turkey.
The history of Judaism in Turkey goes back at least 2,400 years. Today, the Jewish community counts about 25,000, most of whom live in Istanbul, but also considerable communities in Izmir and other major cities.
Turkish Jews are almost all Sephardi, with only about 1,000 Ashkenazi. Turkish Jews are well-organized, and headed by a chief rabbi.