It is necessary to distinguish between Boltzmann’s original lecture notes, his extemporaneous lectures, the fair copy of philosophy lectures 3 to 18 by an unknown hand which are mostly on mathematics, and the multi-published versions which only include lectures 1 and 2. There is a difference between his real thought in his notes (or “honne” in Japanese) and what seems to have survived in lectures 1 and 2 for public consumption (“tatamae”). We have stuck with honne, but where it is (...) too abbreviated to make initial sense, we have put it in grammatical and intelligible form as what we think he most probably intended or believed. It was precisely his linguistic philosophy and the relativistic and pragmatic way of presenting it which was largely suppressed or at least toned-down in the fair copy and published versions. Listeners remembered how witty he was when speaking, and the shortened published accounts are also interesting, but his first thoughts, his honne, before prudence set in will interest most readers, though alas as happens with notes there is also some extraneous material. In translating most of the notes for the first three lectures we have ended where mathematics begins to predominate. (shrink)