"... , writing in ancient Rome around 30 , set out the three elements of architecture as "commodity, firmness, and delight," and no one has done better than his tripartite definition, for it cogently sums up the architectural paradox: a building must be useful while at the same time it must be the opposite of useful, since art—delight, in Vitruvian parlance—by its very essence has no mundane function. And then, on top of all that, a building must be constructed according to the laws of engineering, which is is to say that it must be built to stand up. ... The builders of the , the s, s, and were all engineers as much as architects; to them these disciples were one. So, too, with and his , or at . In our time, the disciplines have diverged, and engineers are not architects. But every great structure of modern times, from 's to 's , is a product of engineers as much as of architects; without firmness, there will be no delight. All three elements of architecture are essential."