In traditional discussion of Jewish Law, you will often see people speak of what Chazal says about a matter. Chazal is not a single person; the term refers collectively to the consensus of authoritative opinion, in much the same way that we might speak of what Congress says or what the Supreme Court says. Chazal is an acronym of the Hebrew phrase Chachameinu Zichronam Liv'racha, which means "our sages of blessed memory" or "our sages, may their memory be a blessing." In its strictest sense, Chazal refers to the final opinion expressed in the Talmud, but the term is sometimes used more loosely to refer to the generally accepted opinion of any of the wise people who have contributed to Jewish law. Throughout this site, I usually use the phrase "the rabbis" where others might use the term Chazal.
These two great scholars born a generation or two before the beginning of the Common Era are usually discussed together and contrasted with each other, because they were contemporaries and the leaders of two opposing schools of thought (known as "houses"). The Talmud records over 300 differences of opinion between Beit Hillel (the House of Hillel) and Beit Shammai (the House of Shammai). In almost every one of these disputes, Hillel's view prevailed.
Rabbi Hillel was born to a wealthy family in Babylonia, but came to Jerusalem without the financial support of his family and supported himself as a woodcutter. It is said that he lived in such great poverty that he was sometimes unable to pay the admission fee to study Torah, and because of him that fee was abolished. He was known for his kindness, his gentleness, and his concern for humanity. One of his most famous sayings, recorded in Pirkei Avot (Ethics of the Fathers, a tractate of the Mishnah), is "If I am not for myself, then who will be for me? And if I am only for myself, then what am I? And if not now, when?" The Hillel organization, a network of Jewish college student organizations, is named for him.
Rabbi Shammai was an engineer, known for the strictness of his views. The Talmud tells that a gentile came to Shammai saying that he would convert to Judaism if Shammai could teach him the whole Torah in the time that he could stand on one foot. Shammai drove him away with a builder's measuring stick! Hillel, on the other hand, converted the gentile by telling him, "That which is hateful to you, do not do to your neighbor. That is the whole Torah; the rest is commentary. Go and study it."
Rabbi Yochanan ben Zakkai was the youngest and most distinguished disciple of Rabbi Hillel (see above). He has been called the "father of wisdom and the father of generations (of scholars)" because he ensured the continuation of Jewish scholarship after Jerusalem fell to Rome in 70 C.E.
According to tradition, ben Zakkai was a pacifist in Jerusalem in 68 C.E. when the city was under siege by General Vespasian. Jerusalem was controlled by the Zealots, people who would rather die than surrender to Rome (these are the same people who controlled Masada). Ben Zakkai urged surrender, but the Zealots would not hear of it, so ben Zakkai faked his own death and had his disciples smuggle him out of Jerusalem in a coffin. They carried the coffin to Vespasian's tent, where ben Zakkai emerged from the coffin. He told Vespasian that he had a vision (some would say, a shrewd political insight) that Vespasian would soon be emperor, and he asked Vespasian to set aside a place in Yavneh (near modern Rehovot) where he could move his yeshiva (school) and study Torah in peace. Vespasian promised that if the prophecy came true, he would grant ben Zakkai's request. Vespasian became Emperor and kept his word, allowing the school to be established after the war was over. The yeshiva survived and was a center of Jewish learning for centuries.
A poor, semi-literate shepherd, Rabbi Akiba became one of Judaism's greatest scholars. He developed the exegetical method of the Mishnah, linking each traditional practice to a basis in the biblical text, and systematized the material that later became the Mishnah.
Rabbi Akiba was active in the Bar Kokhba rebellion against Rome. He believed that Bar Kokhba was the Mashiach (messiah), though some other rabbis openly ridiculed him for that belief (the Talmud records another rabbi as saying, "Akiba, grass will grow in your cheeks and still the son of David will not have come.") When the Bar Kokhba rebellion failed, Rabbi Akiba was taken by the Roman authorities and tortured to death.
The Patriarch of the Jewish community, Rabbi Judah Ha-Nasi was well-educated in Greek thought as well as Jewish thought. He organized and compiled the Mishnah, building upon Rabbi Akiba's work.
A grape grower living in Northern France, Rashi wrote the definitive commentaries on the Babylonian Talmud and the Bible. Rashi pulled together materials from a wide variety of sources, wrote them down in the order of the Talmud and the Bible for easy reference, and wrote them in such clear, concise and plain language that it can be appreciated by beginners and experts alike. Almost every edition of the Talmud printed since the invention of the printing press has included the text of Rashi's commentary side-by-side with the Talmudic text. Many traditional Jews will not study the Bible without a Rashi commentary beside it.
A physician born in Moorish Cordoba, Rambam lived in a variety of places throughout the Moorish lands of Spain, the Middle East and North Africa, often fleeing persecution. He was a leader of the Jewish community in Cairo. He was heavily influenced by Greek thought, particularly that of Aristotle.
Rambam was the author of the Mishneh Torah, one of the greatest codes of Jewish law, compiling every conceivable topic of Jewish law in subject matter order and providing a simple statement of the prevailing view in plain language. In his own time, he was widely condemned because he claimed that the Mishneh Torah was a substitute for studying the Talmud.
Rambam is also responsible for several important theological works. He developed the 13 Principles of Faith, the most widely accepted list of Jewish beliefs. He also wrote the Guide for the Perplexed, a discussion of difficult theological concepts written from the perspective of an Aristotelian philosopher.
Ramban was the foremost halakhist of his age. Like Rambam before him, Ramban was a Spaniard who was both a physician and a great Torah scholar. However, unlike the rationalist Rambam, Ramban had a strong mystical bent. His biblical commentaries are the first ones to incorporate the mystical teachings of kabbalah.
He was well-known for his aggressive refutations of Christianity, most notably, his debate with Pablo Christiani, a converted Jew, before King Jaime I of Spain in 1263.
Ramban could be described as one of history's first Zionists, because he declared that it is a mitzvah to take possession of Israel and to live in it (relying on Num. 33:53). He said, "So long as Israel occupies [the Holy Land], the earth is regarded as subject to Him." Ramban fulfilled this commandment, moving to the Holy Land during the Crusades after he was expelled from Spain for his polemics. He found devastation in the Holy Land, "but even in this destruction," he said, "it is a blessed land." He died there in 1270 C.E.
Do not confuse Ramban with Rabbi Nachman of Breslov (see below).
The founder of Chasidic Judaism. Although many books of his teachings exist, the Besht himself wrote no books, perhaps because his teachings emphasized the fact that even a simple, uneducated peasant could approach G-d (a radical idea in its time, when Judaism emphasized that the way to approach G-d was through study). He emphasized prayer, the observance of commandments, and ecstatic, personal mystical experiences.
The great-grandson of the Baal Shem Tov (see above), Rabbi Nachman of Breslov (sometimes called Bratzlav, Breslau or Bratislava) was the founder of the Breslover Chasidic sect. Breslov is a town in the Ukraine where Rabbi Nachman spent the end of his life, but some say the name Breslov comes from the Hebrew bris lev, meaning "covenant of the heart." He emphasized living life with joy and happiness. One of his best-known sayings is, "It is a great mitzvah to be happy." Collections of his Chasidic tales (or tales attributed to him) are widely available in print.
Do not confuse Rabbi Nachman with Ramban (see above).