Nahmanides, also known as Rabbi Moses ben Nachman Girondi, and by his Hebrew acronym "Ramban" (Rabbi Moshe ben Nachman), was a leading medieval Jewish scholar, Catalan rabbi, philosopher, physician, kabbalist, and biblical commentator. "Nahmanides" is a Greek-influenced formation meaning "son of Nachman". His Catalan name was Bonastruc Sa Porta. Nahmanides was born at Girona (hence his name "Girondi") in 1194, and died in the Land of Israel about 1270. He was the grandson of Isaac ben Reuben of Barcelona and cousin of Jonah Gerondi (the Rabbeinu Yonah). His brother was Benveniste de Porta, the bailie of Barcelona. Among his teachers in Talmud were Judah ben Yakkar and Meïr ben Nathan of Trinquetaille, and he is said to have been instructed in Kabbalah (Jewish mysticism) by his countryman Azriel of Gerona, who was in turn a disciple of Isaac the Blind.

Nahmanides studied medicine which he practiced as a means of livelihood. He also studied philosophy. During his teens he began to get a reputation as a learned Jewish scholar. He learnt from the famous kabbalist Zacharia Coppell Gold. At age 16 he began his writings on Jewish law. In his Milhamot Hashem (Wars of the Lord) he defended Alfasi's decisions against the criticisms of Zerachiah ha-Levi of Girona. These writings reveal a conservative tendency that distinguished his later works, an unbounded respect for the earlier authorities. In the view of Nahmanides, the wisdom of the rabbis of the Mishnah and Talmud, as well as the Geonim (rabbis of the early medieval era) was unquestionable. Their words were to be neither doubted nor criticized. "We bow," he says, "before them, and even when the reason for their words is not quite evident to us, we submit to them". Soon after the appearance of Maimonides' Guide for the Perplexed, a tendency to allegorize Biblical narratives arose to downplay the role of miracles. Against this tendency Nahmanides strove, and went to the other extreme, not even allowing the utterances of the immediate disciples of the Geonim to be questioned.

Called upon, about 1238, for support by Solomon of Montpellier, who had been excommunicated by supporters of Maimonides, Nahmanides addressed a letter to the communities of Aragon, Navarre, and Castile, in which Solomon's adversaries were severely rebuked. In a letter addressed to the French rabbis, he draws attention to the virtues of Maimonides and holds that Maimonides' Mishne Torah, his Code of Jewish Law, not only shows no leniency in interpreting prohibitions within Jewish law, but may even be seen as more stringent, which in Nahmanides' eyes was a positive factor. As to Maimonides' Guide for the Perplexed, Nahmanides stated that it was intended not for those of unshaken belief, but for those who had been led astray by the non-Jewish philosophical works of Aristotle and Galen. "If," he says, "you were of the opinion that it was your duty to denounce the Guide as heretical, why does a portion of your flock recede from the decision as if it regretted the step? Is it right in such important matters to act capriciously, to applaud the one today and the other tomorrow?"

In Nahmanides's Torat ha-Adam, which deals with mourning rites, burial customs, etc., Nahmanides sharply criticizes writers who strove to render man indifferent to both pleasure and pain. This, he declares, is against the Law, which commands man to rejoice on the day of joy and weep on the day of mourning. The last chapter, entitled Shaar ha-Gemul, discusses reward and punishment, resurrection, and kindred subjects. It derides the presumption of the philosophers who pretend to a knowledge of the essence of G-d and the angels, while even the composition of their own bodies is a mystery to them. For Nahmanides, divine revelation is the best guide in all these questions, and proceeds to give his views on Jewish views of the afterlife. He holds that as G-d is eminently just, there must be reward and punishment. This reward and punishment must take place in another world, for the good and evil of this world are relative and transitory.

Besides the animal soul, which is derived from the "Supreme powers" and is common to all creatures, man possesses a special soul. This special soul, which is a direct emanation from G-d, existed before the creation of the world. Through the medium of man it enters the material life, and at the dissolution of its medium it either returns to its original source or enters the body of another man. This belief is, according to Nahmanides, the basis of the levirate marriage, the child of which inherits not only the name of the brother of his fleshly father, but also his soul, and thus continues its existence on the earth. The resurrection spoken of by the prophets, which will take place after the coming of the Messiah, is referred by Nahmanides to the body. The physical body may, through the influence of the soul, transform itself into so pure an essence that it will become eternal.

His commentary on the Torah (five books of Moses) was his last work, and his most well known. It frequently cites and critiques Rashi's commentary, and it usually provides alternative interpretations. He was prompted to write it by three motives: (1) To satisfy the minds of students of the Law and stimulate their interest by a critical examination of the text. (2) To justify the ways of G-d and discover the hidden meanings of the words of Scripture, "for in the Torah are hidden every wonder and every mystery, and in her treasures is sealed every beauty of wisdom." (3) To soothe the minds of the students by simple explanations and pleasant words when they read the appointed sections of the Pentateuch on Sabbaths and festivals.

His commentary on the creation of the world describes the universe expanding, and matter forming. "At the briefest instant following creation all the matter of the universe was concentrated in a very small place, no larger than a grain of mustard. The matter at this time was very thin, so intangible, that it did not have real substance. It did have, however, a potential to gain substance and form and to become tangible matter. From the initial concentration of this intangible substance in its minute location, the substance expanded, expanding the universe as it did so. As the expansion progressed, a change in the substance occurred. This initially thin noncorporeal substance took on the tangible aspects of matter as we know it. From this initial act of creation, from this etherieally thin pseudosubstance, everything that has existed, or will ever exist, was, is, and will be formed."

While Maimonides endeavored to reduce the miracles of the Bible to the level of natural phenomena, Nahmanides emphasizes them, declaring that "no man can share in the Torah of our teacher Moses unless he believes that all our affairs, whether they concern masses or individuals, are miraculously controlled, and that nothing can be attributed to nature or the order of the world." Next to belief in miracles Nahmanides places three other beliefs, which are, according to him, the Jewish principles of faith, namely, the belief in creation out of nothing, in the omniscience of G-d, and in divine providence.

Nahmanides, first as rabbi of Girona and later as chief rabbi of Catalonia, seems to have led a largely untroubled life. When well advanced in years, however, his life was interrupted by an event which made him leave his family and his country and wander in foreign lands. This was the religious disputation known as the Disputation of Barcelona of 1263 in which he was called upon to defend his faith in 1263. The disputation concluded in a complete victory for Nahmanides, but because of this victory he was eventually sentenced to exile into perpetual banishment.

Nahmanides left Aragon and sojourned for three years somewhere in Castille or in southern France. In 1267, seeking refuge in Muslim lands from Christian persecution, he made aliyah to Jerusalem. There he established a synagogue in the Old City that exists until present day, known as the Ramban Synagogue. His re-establishment of Jewish communal life in Jerusalem (which had been interrupted by Crusader repression) is notable in that it marked the beginning of almost 700 consecutive Jewish years in Jerusalem until the 1948 Arab-Israeli War. Nahmanides then settled at Acre, where he was very active in spreading Jewish learning. It was to arouse the interest of the Israeli Jews in the exposition of the Bible that Nahmanides wrote the greatest of his works, the commentary on the Torah. Although surrounded by friends and pupils, Nahmanides keenly felt the pangs of exile. "I left my family, I forsook my house. There, with my sons and daughters, the sweet, dear children I brought up at my knees, I left also my soul. My heart and my eyes will dwell with them forever."

Nahmanides died after having passed the age of seventy-six. There is a disagreement as to his actual burial place. Some say that his remains were interred at Haifa. Others say that they are as he requested, next to the building housing the grave sites of the Patriarchs and Matriarchs in Hebron. Supporting this latter theory was the discovery of a small underground tomb in the exact place that his request mentioned, under the seventh step of the small stairs to the right of the building. This location is visited at times by people to give respect to this great Torah Master.

Nahmanides wrote glosses on the whole Talmud and made compendiums of parts of Jewish law. His major work on the Talmud is referred to as: "Chiddushei haRamban", and offers a dazzling breadth and depth to the Talmud. He often provides a different perspective on a variety of issues that are addressed by the Tosefot. Nahmanides' known halakhic works are: "Mishpetei ha-Cherem," the laws concerning excommunication, "Hilkhot Bedikkah," on the examination of the lungs of slaughtered animals, and "Torat ha-Adam," on the laws of mourning and burial ceremonies.

Nahmanides' writings in the defense of Simeon Kayyara and Alfasi also belong in the category of his Talmudic and halachic works. These writings are: "Milhamot HaShem," "Sefer ha-Zekhut," and "Hassagot." Other works include: "Sefer ha-Mitzwoth", "Derashah", "Sefer ha-Ge'ulah", or "Sefer Ketz ha-Ge'ulah", on the time of the arrival of the Messiah, "Iggeret ha-Musar", ethical letter addressed to his son, "Iggeret ha-Chemdah", letter addressed to the French rabbis in defense of Maimonides, "Vikuach", religious argument of 1263, and "Perush Iyyov", and "Perush al ha-Torah."