  Next, in the 1890s the reversibility problem resurfaced again, this time in a debate in the columns of Nature.  This time Boltzmann chose an entirely different line of counterargument than in his debate with Loschmidt. A few years later, Zermelo presented another objection, now called the recurrence objection. The same period also saw the publication of the two volumes of his Lectures on Gas Theory. In this book, he takes the hypothesis of molecular disorder (a close relative of the SZA) as the basis of his approach. The combinatorial argument is only discussed as an aside, and the ergodic hypothesis is not mentioned at all. His last paper is an Encyclopedia article with Nabl presenting a survey of kinetic theory.