The Road is one of the great fundamental institutions of mankind. Not only is the Road one of the great human institutions because it is fundamental to social existence, but also because its varied effects appear in every department of the State. It is the Road which determines the sites of many cities and the growth and nourishment of all. It is the Road which controls the development of strategies and fixes the sites of battles. It is the Road that gives its framework to all economic development. It is the Road which is the channel of all trade, and, what is more important, of al ideas. In its most humble function it is a necessary guide without which progress from place to place would be a ceaseless experiment; it is a sustenance without which organized society would be impossible, thus the Road moves and controls all history. – Hilaire Belloc.
In this paragraph, the first sentence states the subject. It is the topical sentence. The body of the paragraph consists of examples which prove the statement in the first sentence. The final sentence sums up the whole.