A word respecting the author's method Of quoting may not be out Of place. In the majority of cases, the quotations serve, in the usual way, as documentary evi dence in support of assertions made in the text. Butin many instances, passages from economic writers are quoted in order to indicate when, where, and by whom a certain proposition was for the first time clearly enunciated. This is done in cases where the proposition quoted is Of im portance as beinga more or less adequate expression of the conditions Of social production and exchange prevalent at the time, and quite irrespective Of Marx's recognition, or otherwise, of its general validity. These quotations, therefore, supplement the text by a running commentary taken from the history Of the science.