This work offers a contextual comparative analysis of commercial contracts from their origin until the present time. It studies their positive and living law in countries and regions representative of major legal systems and business cultures: Classical Rome, Medieval Europe and the Middle East, Codification Europe (especially France and Germany), Post-Colonial Latin America, the Soviet Union, the Peoples' Republic of China, England (eighteenth and nineteenth centuries), and Post-Colonial United States. It identifies contractual concepts, principles, rules, doctrines, methods of reasoning and commercial practices that have contributed most to mankind's economic development. Finally, it explains how certain selfish and altruistic components of standard and fiduciary commercial and financial practices combine to cause the necessary trust and cooperation that makes possible both economic growth and legal institutional longevity.