This provides an analytical proof of the Second Law in a way completely different from those attempted so far. Up till now, one has attempted to proof that \(\int dQ/T = 0\) for reversible (umkehrbaren) cyclic[12] processes, which however does not prove that for an irreversible cyclic process, which is the only one note-that occurs in nature, it is always negative; the reversible process being merely an idealization, which can be approached more or less but never perfectly. Here, however, we immediately reach the result that \(\int dQ/T\) is in general negative and zero only in a limit case… (WA I, 345)