The mainthesis of this book is that Milton is similarly changeless, and that one set of notions runs through all of his works, from lyrics composed in the 1630s to his epic poetry of the 1660s.
His mainthesis is that the buzz of urban life, and the opportunities it offers for co-operation and collaboration, is what attracts people to the city, which in turn makes cities into the engines of art, commerce, science and progress.