Just thirty years after George Plekhanov’s death, which occurred in Finland on June 12, 1918, an English translation of his principal philosophical essay has appeared under the title In Defence of Materialism. 1 Plekhanov was a prolific writer. But the twenty-four volume edition of his works, published in Moscow in the nineteen-twenties, is no longer easy to come by; and only a few of his essays and articles had hitherto been available in English. The present translation has been entrusted to the safe hands of Mr. Andrew Rothstein. It is preceded by an introductory sketch which is as accurate and masterly an account as could be desired of Plekhanov’s career and significance.