  Boltzmann was involved in various disputes. But this is not to say that he was the innocent victim of hostilities. In many cases he took the initiative by launching a polemic attack on his colleagues. I will focus below on the most important disputes: with Mach and Ostwald on the reality of atoms; and with colleagues who criticized Boltzmann's own work in the form of the famous reversibility objection (Loschmidt) and the recurrence objection (Zermelo). For a wider sketch of how contemporary scientists took position in the debate on the topics of mechanism and irreversibility I refer to (van Strien 2013).  