alian merchants developed commercial and financial techniques, such as bookkeeping and bills of exchange. The creation of the public debt, a concept unknown in ancient times, allowed these cities to finance their territorial expansion through military conquest. Their merchants controlled commerce and finance across Europe. This fluid mercantile society contrasted sharply with the rural, tradition-bound society of medieval Europe; it was less hierarchical and more concerned with secular objectives. The recovery and study of the classics entailed the creation of new disciplinesclassical philology and archaeology, numismatics, and epigraphyand critically affected the development of older ones. In art, the decisive break with medieval tradition occurred in Florence about 1420 with the invention of linear perspective, which made it possible to represent three-dimensional space on a flat surface. The works of the architect Filippo Brunelleschi and the painter Masaccio are dazzling examples of the uses of this technique.Donatello, who is considered the founder of modern sculpture, created the bronze David, the first life-size nude since antiquity. From the mid-15th century on, classical form was rejoined with classical subject matter, and mythological motifs derived from literary sources adorned palaces, walls, furniture, and plates. The ancient practice of striking medals to commemorate eminent figures such as the Florentine statesman Cosimo de' Medici was reintroduced by Pisanello. Portraits of notable figures, emphasizing individual characteristics, were painted by Piero Della Francesca, Andrea Mantegna, and Sandro Botticelli. The Renaissance ideals of harmony and proportion culminated in the works of Raphael, Leonardo da Vinci, and Michelangelo in the 16th century. In medicine and anatomy, progress was made, especially after the first translation of many ancient works of Hippocrates and Galen in the 15th and 16th centuries. Some of the m...
