May I take my last difficulty first? A traveller, he was an American, was asked what he thought of Rome. "I guess," he answered, "it'll be a nice place when it is finished." This was a trans-Atlantic way of restating the old saying that Rome wasn't built in a day. It certainly was not. Rome had been Rome-building for 25 centuries when this good man made his observation, and it is probable that she will be still hard at work with bricks and mortar (or ferro-concrete) when this poor planet utters the first rumblings of dissolution.
Apart from all questions of growth of population, of traffic needs, and of city improvements, there goes on in every town a ceaseless substitution of new for old, which is so persistent that ordinary humanity does not even notice it. Very few folk observe the fact that the show streets of their favourite town are perpetually unfinished. If they do observe it at all, they will assure you that the prevailing scaffold-poles are merely temporary, and that everything will be straight and tidy by next season. They would honestly mean what they say, but you and I know that the time of tidiness will never come unless it is brought about by an age of universal poverty and apathy. So long as there is health there is wealth; so long as there is wealth there is change. And if things beautiful and old are spared who should complain? Certainly not an architect.
So here, at least, is one factor—perpetual flux—that defeats the theoretic town-planner.
And here is another, coming under my first heading, that, whatever planners may plan, there are certain laws