which is the true religion?

Because religions are so different, only one could be the "true religion." Perhaps none are. Within the "true religion" there may be more than one faith group that are sufficiently accurate in their beliefs and practices that all could qualify as "true." The problem is how to find out which religion and which faith groups have this status.

Some methods of determining the "true" religion are:

	Conduct an opinion poll: Unfortunately, beliefs differ around the world: In Saudi Arabia, the government claims that 100% of the population is Muslim. So there is probably a very high probability that a given citizen picked at random would firmly believe Islam is the true religion and that theirs is the true faith group. India is about 80% Hindu. There is a very high probability that any given citizen believes that their tradition with Hinduism is the true religion. The U.S. is about 75% Christian. The population in the American "Bible belt" is significantly higher than that. There is a very high probability that any given citizen in South Carolina, for example, believes that their denomination within Christianity is the true religion. It is obvious that one's personal beliefs about the true religion is largely a function of the country in which one happens to have been born, the area of that country, and the beliefs of one's parent(s):  If Jerry Falwell had been born in Saudi Arabia of Muslim parents, and obtained his religious education in that country, there is a near certainty that he would be promoting Islam today. If the late Sheikh Mohamed Mutwali al-Sharawilittle of Egypt, who was called "The Arab world's best known television preacher of the Holy Qur'an," had been born and raised by Southern Baptists in Dallas, TX, that he would almost certainly have promoted Christianity. One's personal beliefs and the certainty with which one holds them is an unreliable measure of truth, because they are largely determined by one's culture and the faith of one's parents -- both largely accidents of birth. So, an opinion poll might show what peoples beliefs are. But it would not be helpful in locating the "true" faith group.
	Pray to God 5 and ask to be enlightened. The founder of the Mormon movement, Joseph Smith, did precisely this. Mormons believe that God and Jesus Christ appeared to him side by side, and told him that none of the then existing Christian denominations were the true religion. He was instructed to create a new denomination to restore Christianity to its first century CE purity before it fell into heresy. This method appears to be unreliable. When people pray to God for enlightenment, most seem to conclude that their own religion and faith group is the true one. If people could access the will of God on this matter, then a vast majority of the world's population -- the folks who pray -- would realize that their faith group was not the true one. They would gradually migrate to the true religion. There would eventually be only one religion and one tradition within that religion left standing. Otherwise, people would be rejecting the will of God. All the other 11,000 religions and their tens of thousands of denominations or traditions would be phased out. The OCRT, the group that sponsors this web site, conducted a pilot study to determine whether a person can assess the will of God through prayer. We used a controversial topic: whether God favors same-sex marriage for homosexuals and some bisexuals. The answer that we found was that people appear to be unable to assess the will of God through prayer.
	Communication from God: God could initiate a direct communication to humanity. In order to be convincing, it would have to be totally unambiguous, clear and convincing. One example might be for God to rearrange a few thousand stars to spell out in the evening sky the name of the true religion. Unfortunately, at least within the Judeo-Christian traditions, God seems to be progressively withdrawing from humanity. He walked in person with Adam and Eve. Later, he only appeared in rare occasions as at Mount Sinai. Still later, he communicated with humans only through prophets. Most Christians believe that Jesus Christ is God and walked among humans in first centuryCE Palestine. However, he was seen by only a miniscule percentage of the human race. Now, access to God is through prayer.

Unless God were to take the initiative, it appears that there is no way for humans to determine which religion is "true."

source: http://www.religioustolerance.org/reltrue.htm