1092-1167

Spanish Jewish scholar who wrote on a number of mathematical topics, introducing Europeans to concepts that originated in the Arab world. Ezra spent the first five decades of his life peacefully, but after 1140 political turmoil forced him to wander throughout Christian Europe. In his latter years, when he lived in Italy, he wrote his most important works, among them treatises whose titles are rendered in English as Book of the Unit and Book of the Number. The first concerned the Hindu-Arabic numerals 1 through 9, and the second the decimal system. Ezra discussed the concept of zero, which he called galgal, meaning circle. In spite of the attention directed toward his work, it would still be several centuries before the Hindu-Arabic system gained widespread acceptance in Europe.