When Karl Marx died in 1883, he left behind a huge if fragmented opus along with a revolutionary new perspective of society. Yet his ideas were initially of limited influence; it was not until the following decades that their enormous impact came into play. How did this come about? Taking as examples nine committed intellectuals from all parts of Europe – including Rosa Luxemburg, Karl Kautsky, Eduard Bernstein and Wladimir Ilyich Lenin – the lecture demonstrates how Marx's ideas were taken up and spread throughout Europe. Thus, a theory to describe social reality in capitalism grew into that political philosophy that was to spread in the 20th century as a (state) ideology – inspiring one of the most influential and consequential political movements in modern times.