To understand Christianity and Islam, you first have to understand Judaism — the shared root of all three Abrahamic faiths. It is also one of the oldest continuous monotheisms: a people that has never exceeded 0.2% of the world's population, yet wrote ideas like "one God," "history has a direction," and "humans bear moral responsibility for the world" into the operating system of half the planet.
"Hear, O Israel: the Lord our God, the Lord is One."— The Shema, Deuteronomy 6:4, the central declaration of Jewish faith
Judaism's story begins with the covenant of Abraham: traditionally around 1800 BCE, Abraham enters into a covenant with God, the starting point of monotheistic faith. Then comes Moses and the Exodus — at Mount Sinai the people receive the Torah (literally "teaching / instruction"), and the covenant expands from a family to a whole nation. (The historicity of the Exodus remains debated archaeologically, but its status as the founding narrative is irreplaceable.)
What follows is a history of "Temple and dispersion" cycles. Around the 10th century BCE, Solomon builds the First Temple in Jerusalem; in 586 BCE the Babylonians destroy it and deport the elite — the "Babylonian exile." The rebuilt Second Temple is destroyed by the Romans in 70 CE — a decisive moment: with the Temple and its sacrificial center gone, Judaism is forced to reinvent itself.
Rabbis (teachers) replace priests; the synagogue replaces the Temple, and study and prayer replace sacrifice. The oral law is written down as the Mishnah (c. 200 CE) and the Talmud (c. 500 CE) — a vast compendium of debate still studied page by page today. It is precisely this "rabbinic Judaism" that let a landless people endure for nearly two thousand years.
The Middle Ages split Jewry into two great branches, Ashkenazi (Central/Eastern Europe) and Sephardi (Spain, the Mediterranean); the expulsion from Spain came in 1492. The modern era brought the Enlightenment (Haskalah), anti-Jewish violence (pogroms), and finally the Holocaust — some six million Jews murdered by the Nazis, European Jewish civilization nearly torn out by the roots. In 1948 the State of Israel is founded, giving the two-millennia-old prayer "next year in Jerusalem" a concrete anchor — and opening new tensions.
The global Jewish population is roughly 15 million (14.7–15.7 million depending on definition), about 0.2% of the world — among the smallest of the major religions. It is highly concentrated at two poles:
The key point: Jewish identity is doubly "ethnic-and-religious" (an ethnoreligion). One can be a "secular Jew" — Jewish by culture and descent, yet not religiously observant. Traditionally Jewish identity passes through the maternal line (Reform also accepts patrilineal descent); conversion is possible, but Judaism does not actively proselytize and may even discourage converts at first — a sharp contrast with Christianity and Islam, and part of why its numbers have always stayed small.
Judaism is strict monotheism: God is one, formless, indivisible (precisely what the Shema declares). The core is not "which doctrines you believe" but covenant (brit) — God chooses the people of Israel, the two enter a pact, and the people respond to God's grace by keeping the commandments.
"Chosen people" is often misread as superiority; it in fact means responsibility, not privilege: chosen to carry the Torah, to be "a light unto the nations." Tradition even says God offered the Torah to every nation, and only Israel accepted the burden.
Jewish spirituality lies not in solitary contemplation but in sanctifying every part of life through countless concrete acts (mitzvot, commandments). Tradition counts 613 commandments. Core practices include:
Misconception: "chosen" means Jews consider themselves superior.
It means responsibility, not superiority — chosen to keep the law and carry the moral burden. Traditional texts stress repeatedly that this is a weight, not a reward.
Misconception: Judaism is just "Old Testament Christianity."
Their theologies differ greatly: Judaism has no original sin or Trinity, the Messiah has not yet come, and its living tradition is the rabbinic Talmud, not the Christian New Testament.
Misconception: all Jews are religiously observant.
Jewish identity is both ethnic and religious. Both Israel and the US have large numbers of "secular Jews" who identify culturally but do not practice.
Misconception: Judaism equals Zionism.
The former is a religious tradition; the latter a political-national movement that arose in the 19th century. They are related but not identical, and Jews hold extremely diverse, often conflicting, views on Israeli policy.
Three faiths, one source. Judaism is the matrix of Christianity and Islam: Jesus was a Jew, and the Qur'an recognizes Abraham and Moses as prophets. The three share a skeleton of one God, prophets, covenant, and eschatology, yet part ways over "has the Messiah come?" and "did God become incarnate?" Grasp Judaism and the next issues (Day 2–8) go much more smoothly.
Underrated intellectual export. "History has a direction rather than cycles," "redemption will come within time," "humans bear moral responsibility for society" — these premises seep into Western law, ethics, and even secular ideas of progress, and their source often lies here.
Tensions today. The trauma of Holocaust memory, the complex relationship between Israel and the diaspora, resurgent antisemitism, debates over secularization and intermarriage — how Judaism holds onto itself between "continuity" and "adaptation" is a question two thousand years old and still unfinished.
This piece introduces Judaism from a neutral, comparative standpoint, aiming to present its internal logic and diversity without praise or ranking. Figures are recent estimates and vary by range because definitions (religion vs. ethnic identity) differ.