Separation of church and state
The separation of church and state is the principle that religion and government have separate roles, and that neither should intrude upon the other: religious organizations may not set government policy, and the government may not privilege one religion over another, or religion in general over non-religion (and vice-versa). It is an important concept in secularism and a requirement of an "open society". The opposite policy is referred to as the "establishment of religion" as the official state sanctioned belief. When a religion gains significant influence in government, that government is referred to as a theocracy.
Consequences of religious influence
Coercion in religion and propaganda
If a religion can establish itself as the state religion, it can coerce people into participation. This includes mandating religious worship in prisons  or everyday life. Drug recovery programs with religious content can be mandated.  Teacher led prayers or repeated references to God can be introduced in government controlled schools.
Holidays are state sanctioned and typically aligned to a particular religion's festivals.
Many countries supposedly have laws or constitutional measures to prevent people being coerced by the state into a particular religion but their governments attempt to establish an official religion regardless.
Religiously motivated laws
Religion can motivate laws, their drafting or the way they are implemented. This sometimes occurs without the support of citizens or ignores the needs of minority groups.
Religions dogma can motivate preferential treatment for a particular group, such as Arab Israelis being treated as second class citizens  or preferential treatment of Muslims in Indonesia.  In an Islamic state, non-Muslims (dhimmī) are required to pay a special Jizya tax. These laws often abridge political and personal rights, including:
Suppression of science and history
Education ignores important scientific (e.g. evolutionary) and historical subjects and may be replaced by religious dogma.
The government is more likely to pursue of ineffective policy based on dogma.
- Climate change denial based on religion,
- Abstinence-only sex education or no sex education at all,
- Banning abortion, although this does not significantly reduce the number of abortions.
Religious tests for office
Some countries require religious tests to hold public office or to be a competent witness in a court of law. This even occurs in several US states  but this is usually an ignored technicality since the US Supreme Court ruled that religious tests are unconstitutional.
In an Islamic state, non-Muslims (dhimmī) are not allowed authority over Muslims.
Arguments for separation
Religious government tends towards tyranny
"Is there any maxim in politics more certain and infallible, than that both the number and authority of priests should be confined within very narrow limits; and that the civil magistrate ought, for ever, to keep his fasces [bound wooden bundle symbolising judicial authority] and axes from such dangerous hands? But if the spirit of popular religion were so salutary to society, a contrary maxim ought to prevail."
"Theocracy is the worst of all governments. If we must have a tyrant, a robber baron is far better than an inquisitor."
"History, I believe, furnishes no example of a priest-ridden people maintaining a free civil government."
Religious duties are separate from politics
"Believing with you that religion is a matter which lies solely between Man & his God, that he owes account to none other for his faith or his worship, that the legitimate powers of government reach actions only, & not opinions, I contemplate with sovereign reverence that act of the whole American people which declared that their legislature should 'make no law respecting an establishment of religion, or prohibiting the free exercise thereof,' thus building a wall of separation between Church and State."
- — Thomas Jefferson
- "Then Jesus said to them, "Give back to Caesar what is Caesar's and to God what is God's." And they were amazed at him."
Jesus also showed little interest in worldly affairs such as politics and is generally regarded as a role model for Christians.
Politics corrupts religion
The merging of religion and politics leads to politicians influencing religious affairs. This is generally undesirable even for religious believers. 
Countries that support secularism
- Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof....
The phrase "separation of church and state" does not appear in the Constitution itself; it was first coined by Thomas Jefferson in a letter to the Danbury Baptist Church, to explain the intended effect of this part of the First Amendment.
- It has a legitimate secular purpose, and
- Its primary effect neither advances nor inhibits religion, and
- It does not cause an excessive entanglement between government and religion.
Section 116 of the Australian constitution states:
- The Commonwealth shall not make any law for establishing any religion, or for imposing any religious observance, or for prohibiting the free exercise of any religion, and no religious test shall be required as a qualification for any office or public trust under the Commonwealth.
Article 2 of the French constitution states:
- France is an indivisible, secular, democratic, and social Republic. It ensures the equality of all citizens before the law, without distinction as to origin, race, or religion. It respects all beliefs.
Article 140 of the Basic Law for the Federal Republic of Germany states:
- The provisions of Articles 136, 137, 138, 139, and 141 of the German Constitution of August 11, 1919 shall be an integral part of this Basic Law.
The referenced article 137 of the 1919 Weimar Constitution begins:
- There is no state church. Freedom to form religious communities is guaranteed. Regarding the unification of religious communities within the Reich territory there are no limitations. Every religious community administrates its own affairs without interference of state or community.
Article 20 of the Japanese constitution states:
- (1) Freedom of religion is guaranteed to all.
- (2) No religious organization shall receive any privileges from the State, nor exercise any political authority.
- (3) No person shall be compelled to take part in any religious act, celebration, rite or practice.
- (4) The State and its organs shall refrain from religious education or any other religious activity.
Article 130 of the Mexican constitution states:
- Congress cannot enact laws establishing or prohibiting any religion.
Article 2, section 6 of the Filipino constitution states:
- The separation of Church and State shall be inviolable.
Article 41 of the Portuguese constitution states:
- The churches and religious communities are separate from the State and free to organize and exercise their own ceremonies and worship.
Article 14 of the Russian constitution states:
- The Russian Federation is a secular state. No religion may be established as a state or obligatory one.
- Religious associations shall be separated from the State and shall be equal before the law.
Article 20 of the South Korean constitution states:
- (1) All citizens enjoy the freedom of religion.
- (2) No state religion may be recognized, and church and state are to be separated.
Other countries that support secularism
Countries that oppose secularism
- Burma (Myanmar)
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- ↑ The Young Turks, Ben Affleck Angrily Defends Islam Against Bill Maher/Sam Harris, 6 Oct 2014