Looking at the sectional unit structure of the book in openlibrary.org I noticed that you can, in fact, use \chapter, \section and (abuse) \subsection to achieve the desired layout.
Using a customized \subsection for the descriptions has the advantage that the titles will be automatically included in the ToC and that you have easy access to the optional argument (useful in case of footnotes in the description, to prevent the footnote material to appear in the ToC).
Below I give you some starting point producing almost exactly the layout of the original book; in particular the hanging indentation of the description in the body of the document and in the ToC entries was easily obtained.
The titlesec package was used to customize the sectional unit headings and the titletoc package was used to customixe the entries in the ToC:
\documentclass{book}
\usepackage[explicit]{titlesec}
\usepackage{titletoc}
\usepackage{etoolbox}
\usepackage{lipsum}
\renewcommand\thesection{\Roman{section}}
\newcommand\periodafter[1]{#1.}
\titleformat{\chapter}[display]
{\normalfont\LARGE\filcenter}{}{0pt}{\periodafter{\MakeUppercase{#1}}}
\titleformat{\section}[display]
{\normalfont\Large\filcenter}{\thesection.}{\ifstrempty{#1}{-10pt}{0.5em}}{\ifstrempty{#1}{}{\periodafter{\MakeUppercase{#1}}}}
\titleformat{\subsection}
{\normalfont\small}{}{0em}{\hangindent=1cm#1}
\titlecontents{chapter}
[0em]
{\addvspace{5pt}\filcenter\scshape\Large}
{\MakeUppercase}
{}
{}[\addvspace{5pt}]
\titlecontents{section}
[0em]
{\filcenter\scshape}
{\contentslabel{1em}}
{}
{}[\addvspace{5pt}]
\titlecontents{subsection}
[0em]
{\hangindent=0.5cm\small}
{}
{}
{\titlerule*[2pc]{.}\contentspage}[\addvspace{10pt}]
\begin{document}
\tableofcontents
\chapter{Ricardo and the old political economy}
\section{}
\subsection{Division of the subject --- Advantages of combining the study of History and Political Economy --- The Deductive Method --- The
Historical Method --- Importance of a discussion of Method --- Laws
and precepts relative --- The Social Problems of the Present to be
borne in mind in studying the history of the Past.}
\lipsum[1-4]
\section{}
\subsection{Division of the subject --- Advantages of combining the study of History and Political Economy --- The Deductive Method --- The
Historical Method --- Importance of a discussion of Method --- Laws
and precepts relative --- The Social Problems of the Present to be
borne in mind in studying the history of the Past.}
\lipsum[1-4]
\chapter{The industrial revolution}
\section{Introductory}
\subsection[Division of the subject --- Advantages of combining the study of History and Political Economy --- The Deductive Method --- The
Historical Method --- Importance of a discussion of Method --- Laws
and precepts relative --- The Social Problems of the Present to be
borne in mind in studying the history of the Past.]{Division of the subject --- Advantages of combining the study of History and Political Economy --- The Deductive Method --- The
Historical Method --- Importance of a discussion of Method --- Laws
and precepts relative --- The Social Problems of the Present to be
borne in mind in studying the history of the Past.\footnote{The
fragment of economic history here printed under the title of
`The Industrial Revolution', a title that Toynbee has himself
selected for a book, of which the following pages contain some
of the raw material, consists of notes of lectures delivered by
Toynbee in the hall of Balliol College, Oxford, between October 1881 and
Midsummer 1882.}}
\lipsum[1-4]
\section{England in 1760 --- Population}
\subsection[Division of the subject --- Advantages of combining the study of History and Political Economy --- The Deductive Method --- The
Historical Method --- Importance of a discussion of Method --- Laws
and precepts relative --- The Social Problems of the Present to be
borne in mind in studying the history of the Past.]{Division of the subject --- Advantages of combining the study of History and Political Economy --- The Deductive Method --- The
Historical Method --- Importance of a discussion of Method --- Laws
and precepts relative --- The Social Problems of the Present to be
borne in mind in studying the history of the Past.\footnote{The
fragment of economic history here printed under the title of
`The Industrial Revolution', a title that Toynbee has himself
selected for a book, of which the following pages contain some
of the raw material, consists of notes of lectures delivered by
Toynbee in the hall of Balliol College, Oxford, between October 1881 and
Midsummer 1882.}}
\lipsum[1-4]
\end{document}
An image of the ToC:
An image of the first page of chapter two:
