day inevitably include sources of error—which deters no one from writing current history.
At the time Marx undertook this work, the said source of error was even far more inevitable. To trace during the revolutionary period, 1848–49, the simultaneous economic transformations, or to maintain a survey of them, was plainly impossible. Precisely so during the first months of the London exile, in the autumn and winter of 1849–50. That was just the time when Marx began this work. But despite these unpropitious circumstances, his thorough knowledge of the economic condition of France, as well as of the political history of that country since the February revolution, enabled him to give a presentation of events, which uncovered their inner connection in a manner not since attained, and which later met, brilliantly, the double test that Marx himself subjected them to.
The first test was occasioned by Marx, since the spring of 1850, again gaining some leisure for economic studies and, as a beginning, taking up the economic history of the last ten years. From the facts themselves it became thoroughly clear to him what, thus far, and from the fractional material at hand, he had half deduced a priori: that the world commercial crisis of 1847 was the real cause of the February and March revolutions, and that the industrial prosperity which arrived gradually in the middle of 1848, coming to full bloom in 1849 and 1850, was the vitalizing factor of the renascent European reaction. This was decisive. While in
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