Columbia subject headings:
Ethics, Modern--20th century.
Humanities--History--20th century.
Natural law--History--20th century.
Philosophy, Modern--20th century.
Harvard subject headings:
Ethics, Modern--20th century.
Humanities--History--20th century.
Natural law--History--20th century.
Philosophy, Modern--20th century.
Princeton subject headings:
Ethics, Modern--20th century.
Humanities--History--20th century.
Natural law--History--20th century.
Philosophy, Modern--20th century.