Below is a clear-cut example of how an individual should resort to smart thinking before converting to a religion. Bulan, the ruler of Khazaria, became converted to Judaism around 740 A.D. His nobles and, somewhat later, his people followed suit. Some details of these events are contained in letters exchanged between Khagan Joseph of Khazaria and R. Hasdai Ibn Shaprut of Cordova, doctor and quasi foreign minister to Sultan Abd al-Rahman, the Caliph of Spain. This correspondence (around 936-950) was first published in 1577 to prove that the Jews still had a country of their own - namely, the Kingdom of Khazaria. Judah Halevi knew of the letters even in 1140. Their authenticity has since been established beyond doubt. According to these Hasdai-Joseph letters, Khagan Bulan decided one day: "Paganism is useless. It is shameful for us to be pagans. Let us adopt one of the heavenly religions, Christianity, Judaism or Islam." And Bulan summoned three priests representing the three religions and had them dispute their creeds before him. But, no priest could convince the others, or the sovereign, that his religion was the best. So the ruler spoke to each of them separately. He asked the Christian priest: "If you were not a Christian or had to give up Christianity, which would you prefer - Islam or Judaism?" The priest said: "If I were to give up Christianity, I would become a Jew." Bulan then asked the follower of Islam the same question, and the Moslem also chose Judaism. This is how Bulan came to choose Judaism for himself and the people of Khazaria in the seventh century A.D., and thereafter the Khazars (sometimes spelled Chazars and Khozars) lived according to Judaic laws. Source: http://www.biblebelievers.org.au/jews.htm