 Another weakening of common knowledge to consider is of course \(m\)th level mutual knowledge. For a high value of \(m, \mathbf{K}^m_N(A)\) might seem a good approximation of \(\mathbf{K}^{*}_N(A)\). However, point (i) above maintains that no arbitrary high value of \(m\) will help for instance with the practical task of achieving coordination, so that the full force of common knowledge is needed. We illustrate the point through the following example, due to Rubinstein (1989, 1992), showing that simply truncating the common knowledge hierarchy at any finite level can lead agents to behave as if they had no mutual knowledge at  all.[32]