In most subjects one generation knocks down what another has built, and one destroys what another has built. Only in mathematics each generation can add a floor to the old building.

——Hankel

　　From 400 AD to around 1100 AD, mathematics in Europe was basically in a state of stagnation. Contemporary mathematics historian M. Klein commented: Roman civilization could not produce mathematics because it paid too much attention to practical and immediately applicable results. The failure of European medieval civilization to produce mathematical results was due to the opposite reason. It did not care about the physical world at all and believed that worldly affairs and problems were unimportant. Christianity valued the life after death and the preparation for it.

　　In addition, the Black Death that broke out in the second half of the fourteenth century killed about one-third of Europe's population and set the entire European civilization back.