In general, the ancient Romans were a practical people. They cared less about philosophy and pure mathematics than the Greeks did. The Romans were the best of the ancient engineers and architects. They were brilliant students of Greek geometry and trigonometry (三角学) , and they applied their knowledge to the construction of fine bridges, roads, aqueducts(渠道) , and public buildings. They knew about the smelting of iron ore, but they used the iron they produced mainly for spears, swords, and shields, rather than for building construction. While the Romans accomplished practical wonders, they did very little theoretical scientific thinking. Because of their frequent wars, many of their inventions were no more than improvements in the design of Greek weapons with which they were familiar. There are two reasons for the Roman neglect of philosophy and pure mathematics. First, they were apparently too busy conquering nearby nations and forming them into a rapidly growing empire to waste much time on abstract thinking. Secondly, they were handicapped (妨碍) by the rigidity of their numerical system. (Try to multiply XI by LVII or to divide CXLIII by IX it simply cannot be done with pencil and paper. ) The Romans did all of their arithmetic on an abacus, the ancient counterpart of the modern computing machine. Their number system discouraged the study of pure mathematics. The author calls the Romans 'practical' because they______.