Show that any ergodic Markov chain with a symmetric transition matrix (i.e., pij = pji) is reversible.
If pij = pji then P has column sums 1. We have seen (Exercise 9 of Section 11.3) that in this case the fixed vector is a constant vector. Thus for any two states si and sj , wi = wj and pij = pji.Thus wipij = wj pji, and the chain is reversible.