The Romans, though vulgar and ostentatious, understood business. They knew how to combine economy and even solidity with display. As Viollet-le-Duc has observed, “They were rich, and they wanted to appear so,”[388] but they strove to attain their end without waste. Therefore they first ran up a cheap core of rubble, bricks, and mortar, which could be put together by rude slave labour under the direction of an engineer and a few overseers; and their squalid interior they afterward veneered with marble, adding, by way of ornament, tier above tier of Greek columns ranged against the walls. That gaudy exterior had nothing whatever to do with the building itself, and could be stripped off without vital injury. From the Greek standpoint nothing could be falser, more insulting to the intelligence, or, in a word, more plutocratic; but the work was sound and durable, and, to a certain degree, imposing from its mass. This system lasted, substantially unimpaired, even to Constantine or until the final migration of capital to the Bosphorus, the only difference between the monuments of the fourth century and the first being that the former are somewhat coarser, just as the coins of Diocletian are coarser than those of Nero. Yet, although the monied aristocracy remained supreme down to the final disintegration of the West, emigration began very early to modify the base of society, by the injection of a considerable amount of imaginative blood; and, as early as the reign of Claudius, this new store of energy made its presence felt through the outlet of Christianity. The converts were, of course, the antipodes of the ruling class. They were “humiliores,” poor people, below the notice of a rich man like Tacitus; “quos, ... vulgus Christianos appellabat.”[389] These Christians held a position analogous to that of Nihilists now, whom they resembled save in respect to violence. They were socialists living under a monied despotism, and they openly prayed for the end of the world; therefore they were thought “haters of the human race,”[390] and they suffered the penalty. Primitive Christianity was incompatible with the existence of Roman society, against which it was a protest, for it “fully accepted the idea that the rich, if he did not surrender his superfluity, kept what belonged to another.”[391] By right the Kingdom of Heaven was closed to the wealthy.