Israel Scheib was born in 1910 in Eastern Galicia, in a traditional Jewish home. The Scheibs wandered as refugees during the First World War. In 1918, in Lvov, young Scheib witnessed a funeral procession for Jews murdered in a pogrom.

After high school, Scheib enrolled at the Rabbinical Seminary of Vienna for religious studies and the University of Vienna for secular studies. He completed his doctorate on “The Voluntarism of Eduard von Hartmann, Based on Schopenhauer,” but never took his rabbinical exams at the seminary.

Meanwhile, he attended, with his father, a protest demonstration in front of the local British Consulate following the 1929 Arab riots in the Land of Israel. The next year he read a poem by Uri Zvi Greenberg, “I’ll Tell It to a Child,” about a messiah who cannot redeem his people because they are not ready to accept redemption. Two or three years later, Scheib met Greenberg at a speech Greenberg was giving entitled “The Land of Israel Is in Flames.”

Scheib’s first job after graduation was teaching high school in Volkovisk. He also published articles in Revisionist Zionist journals and became the commander of a local Betar chapter.

Scheib joined the staff of the Teachers Seminary in Vilna in 1937, where he stayed for two years. During that time he rose in the Betar ranks to the position of regional staff officer. In 1938, at the Third Betar Conference in Warsaw, when the Revisionist leader Zeev Jabotinsky attacked the militant stance of Poland's Betar leader Menachem Begin, Scheib spoke in Begin's defense. The next year, when the Second World War broke out, Scheib and Begin escaped together from Warsaw. Begin was arrested by the Soviet police in the middle of a chess game with Scheib, and it was several years before they met again in British Mandatory Palestine, where Scheib was already a leader of the Lehi underground and Begin would soon commanded the Irgun. The Lehi was at that point waging a violent struggle for freedom from British rule and the Irgun would, under Begin, soon join the revolt in hopes of turning Palestine into a Jewish state.

Scheib adopted several aliases while living underground, including "Sambatyon" and "Eldad". Eldad stuck and became the name by which he is remembered. He worked in 1942 directly with Lehi founder Avraham Stern. After Stern’s killing by the British, Eldad became one of a triumvirate of Lehi commanders, serving with Natan Yellin-Mor and future prime minister Yitzhak Shamir. It was in this role where Eldad condoned the assassination of Folke Bernadotte, a UN mediator. Yellin-Mor was the diplomatic “foreign minister,” Shamir the operations man, and Eldad the ideologue. For the next six years Eldad wrote articles for various underground newspapers, some of which he edited. Eldad also wrote some of the speeches delivered in court by Lehi defendants.

Eldad was arrested by the British fleeing a Tel Aviv apartment, injured in a fall from a water pipe, and imprisoned in the Jerusalem prison in a body cast. He continued his political and philosophical writing from Cell 18 of the hospital ward at the Jerusalem Central Prison. Eventually Eldad healed enough to escape while on a visit to a dentist’s office, from which several Lehi fighters spirited him away.

During Israel's War of Independence, Eldad was critical of Menachem Begin's Irgun for not defending itself when its arms ship Altalena was attacked by Grün's (David Ben-Gurion) Palmach forces, commanded by Rubitzov (Yitzhak Rabin). He was also critical of the IDF for not fighting harder to conquer Jerusalem’s Old City and critical of Lehi fighters who did not rush to fight in Jerusalem. Towards the end of the war, Eldad disguised himself as a foreign journalist in order to sneak past Israeli military roadblocks and join the battle for Jerusalem.

The Lehi veterans organized politically as the Fighters Party. At one party meeting, Eldad lectured on Sulam, Jacob’s ladder (based on Genesis 28, where Jacob dreams of a ladder uniting heaven and earth), thus beginning the next chapter in his life. For 14 years he published a revolutionary journal, Sulam. Eldad also spent half of 1949 writing his memoirs, entitled Maaser Rishon.

Eldad eventually got a job teaching Bible and Hebrew literature in an Israeli high school, until Prime Minister David Ben-Gurion intervened and had him dismissed. Ben-Gurion was afraid Eldad would imbue the students with his Lehi ideology. Eldad went to court and won, but found few people willing to hire him after Ben-Gurion had labeled him a danger to the state. Eldad turned to literary work, wrote histories of underground battles, a biography of the mayor of Ramat Gan, a newspaper-style review of Jewish history called Chronicles, a book of Bible commentary (Hegionot Mikra), weekly newspaper columns, and many more books, encyclopedia entries and other works. In 1962, Eldad was made a lecturer at the Technion in Haifa. He taught there for twenty years. In 1988, Eldad was awarded Israel’s Bialik Prize for his contributions to Israeli thought.

By the 1990s, Eldad was known as the doyen of Israeli nationalists. He died on the first day of the Hebrew month of Shevat, in January 1996. His funeral was attended by Prime Minister Benjamin Netanyahu, former prime minister Yitzhak Shamir and Knesset Speaker Dov Shilansky. Eldad was buried on the Mount of Olives, at the foot of the grave of his mentor and friend, Uri Zvi Greenberg.

The Israeli settlement Kfar Eldad was named after him.

Eldad did not believe that the creation of the state of Israel was the goal of Zionism. He considered the state a tool to be used in realizing the goal of Zionism, which he called Malkhut Yisrael (the Kingdom of Israel). Eldad sought what he referred to as national redemption, meaning a sovereign Jewish kingdom in the biblical borders of Israel, with all the world’s Jews living there, and the Jewish Temple rebuilt in Jerusalem. Eldad steadfastly refused to give legitimacy to any Jewish presence in the Diaspora, which he felt was doomed to extinction. Nonetheless, in his view of history, past generations of Jews in exile from the Land of Israel were not denigrated as passive sufferers but were considered creative players in history. Eldad and his journal Sulam wrote frequently about Jewish political figures who throughout history tried to bring redemption to their people, but who were stymied by geopolitical or other obstacles.

Eldad called on all Jews to join in the building of Israel, not for their personal fulfillment but because they are needed there.Politically, Eldad favored an independent foreign policy, with Israel not a member of any foreign bloc. He advocated more forceful use of the Israel Defense Forces and opposed the inclusion of the word “defense” in the name of the army. He opposed ceding any land to the Arabs.

Most of Eldad’s voluminous writings have not been translated into English. A few have been: Chronicles ISBN 965-7108-15-2. The Jewish Revolution appeared in 1971, and was reissued in 2007. Free Jerusalem includes a chapter by Eldad (“Meanwhile, A European Interlude”) about Polish Jewry on the eve of war. Israel: The Road to Full Redemption, a translation of an article in Sulam, was published in 1961 and is today a virtually unobtainable brochure. A website is devoted to disseminating articles by Eldad and his underground colleagues. His memoirs of the time he led the underground, The First Tithe, were first translated and published in 2008 ISBN 978-965-416-015-5. God, Man and Nietzsche includes a lengthy examination of Eldad’s philosophy of history and excerpts from an article about Nietzsche written by Eldad in the underground.

Many of Eldad's political and philosophical teachings continue to be espoused by the Magshimey Herut (achievers of liberty) organization, the Zionist Freedom Alliance, and by the Hatikva political party (led by Eldad's son Aryeh) in Israel.