 In 1869 he joined the Zurich faculty as a Privatdozent. He finished the heavily revised second edition of the Arbeiterfrage in 1870. In 1870 he also finally received a professorship at Zurich, though, unfortunately, this happened quite soon after he was diagnosed with cancer. Despite the illness he continued working on the second edition of The History of Materialism (Lange 1873–75). After rejecting offers from Königsberg and Würzburg, he accepted an invitation to take up a professorship at Marburg in 1872. He gave lectures right till the end, but cancer eventually led to his death on 21 November 1875 in Marburg.