An important special case is when the players consider all of their opponents’ strategies possible. It should be clear that a rational player will never choose a strategy that is strictly dominated with respect to \(S_{-i}\). That is, if \(s_i\) is strictly dominated with respect that \(S_{-i}\), then there is no informational context in which it is rational for player \(i\) to choose \(s_i\). This can be made more precise using the following well-known Lemma.