Art has reflected the Christian conception of human nature. Sculpture, which played so great a part in the ancient world, and which was intimately associated with Greek ideals, began to decline rapidly in the Christian era. It lasted longer in the Roman Empire of the East, but in Italy it was almost completely forgotten by the eighth century. Painting survived, but not without undergoing an extraordinary degeneration. All the Italian works of art of the Carlovingian period, displayed the utmost indifference to natural form, and a loss of the sense of harmony and beauty. Later on, Italian art fell lower still. “No one dreamed any longer of studying nature or of observing the human body. An epoch in which the interference of supernatural forces was generally accepted, and in which the conception of the universe was founded on a contrast between the natural and the supernatural, could not admit in its art the rule of natural law or a natural order of events.”[25] The intimate connection between the depreciation of human nature due to Christian doctrine and the inferiority of the art of the middle ages cannot be denied. Taine[26] writes of the period as follows: “If one considers the stained-glass windows or the images in the cathedrals, or the rude paintings, it appears as if the human race had become degenerate and its blood had been impoverished; pale saints, distorted martyrs, virgins with flat chests, feet too long and bony hands, hermits withered and unsubstantial, Christs that look like crushed and bleeding earthworms, processions of figures that are wan, and stiffened, and sad, upon whom are stamped all the deformities of misery and all the shrinking timidity of the oppressed.” The art of the middle ages fell lower and lower until the Renaissance, with its return to the Greek ideal, brought new vigour. The great masters of the Renaissance were in addition scientific men who had studied mathematics and who employed the technique of mensuration; such were Alberti, Leonardo da Vinci, Michel Angelo, and others. The return to the Greek ideals and to nature brought with it the taste for beauty. When the ancient spirit was born again, its influence reached science and even religion, and the Reformation was a defence of human nature. The Lutheran doctrines resumed the principle of a “development as complete as possible, of all the natural powers” of man, and saw in that ideal a guide for humanity. Compulsory celibacy was abolished, and free play was given to all the tendencies in conformity with the laws of nature.[27]