The dominant idea of this book is that of progress.
Morgan hop. produced by special causes.
He thought the scale had universal application or substantially the same in kind, with deviations from uniformity ...
Different branches of the family have evidenced human advancement to different conditions.
Progress is historically true of the entire human family, but not uniformly.
Morgan conceived it as a career of social states arranged in a scale on which man has worked his way up from the bottom.
The dominant idea of this book is that of progress