Kaufmann ends his study of Lequeu by emphasizing that
Lequeu's weird fantasies reveal much of his era to anyone who is interested in the development of the artistic ideas rather than in the struggle for practical improvement. Though he looked back to remote times and remote regions, he was none the less the forerunner of significant trends of the twentieth century. In his era, as at present, unrest and incertitude inspired strange preformances; then as now, expressiveness counted more than formality; then as now great and dignified works emerged from the turmoil. It is not my intention to imply and direct affiliationbetween 1800 and 1900; I am concerned only with the continuity of ideas.
Kaufmann's analysis of Lequeu's work, which began in Vienna, ended in the USA in Philadelphia in 1952, with his Three Revolutionary Architects, Boullée, Ledoux, and Lequeu, published by the American Philosophical Society; and it was in Philadelphia that Marcel Duchamp was, so carefully, to supervise the display of his own principal works.
. . .
Tropological space has thus widened to infinity between Vienna and Philadelphia. Von Lequeu bis Duchamp: Demountable Approximations, which became Duchamp's last major work, served him in the putting together of his most disconcerting work, Etant donnés . . . of 1946-66.