The foundations of our faith is the knowledge that our ancestors did not lie to us. God revealed Himself only once. To our forefathers in Mt. Sinai, 49 days after they left Egypt. This happened approximately 150 generations ago*. And while all other religions base their faith in God on "evidences", we Jews know that God Almighty does not leave any physical evidences of His Presence: there are no pictures taken in Mt Sinai, no stones with a special divine radiation, no left overs of that miracle. But there are witnesses. 600,000 witnesses of God's existence. Yesha'ayah (43:12) considers this explicitly as the nature (and mission) of the Jewish People. atem edai, he said, "You are my witnesses," declares the Lord, "that I am God".
In a good sense, the fate of our belief in God is intertwined with trusting our fathers. We believe in God --and so ironically believe all those religions based on the Hebrew Bible-- because we believe in our fathers. Those who stood and heard the voice of God in Sinai. We trust them. We believe that they transmitted the truth from generation to generation. And by believing in their testimony, we inherited their role as God's witnesses.
* Rabbi Henry Pereira Mendes, Z"L (1852-1937) an American sephardic Rabbi, and one of the rabbis of Congregation Shearit Israel in New York, wrote in his Sefer of Jewish History that, although there are some discrepancies as to what would be the exact equivalent date of the Exodus on the vernacular calendar, he suggests to keep in mind the year 1492 (BCE) a date, he said, very easy to remember for anyone who lives in America. Learn More about Shearit Israel and Rabbi Mendes: http://en.wikipedia.org/wiki/Congregation_Shearith_Israel
Rabbi Yosef Bitton. YMJC | 130 Steamboat Rd. | Great Neck | NY | 11024