 The second response begins with Khinchin’s work. Khinchin (1949) pointed out that the problems of the ergodic programme are due to the fact that it focuses on too general a class of systems. Rather than studying dynamical systems at a general level, we should focus on those cases that are relevant in statistical mechanics. This involves two restrictions. First, we only have to consider systems with a large number of degrees of freedom; second, we only need to take into account a special class of phase functions, the so-called ‘sum functions’. These functions are a sum of one-particle functions, i.e., functions that take into account only the position and momentum of one particle. Under these assumption Khinchin proved that as \(n\) becomes larger, the measure of those regions on the energy  hypersurface[18]  where the time and the space means differ by more than a small amount tends towards zero. Roughly speaking, this result says that for large \(n\) the system behaves, for all practical purposes, as if it was ergodic.