 Finally, we consider the case of existential quantification. When is the expression \(\exists v \psi\) satisfied by a team? In order to answer this, we may begin by considering the interpretation of the restriction operator which, given any team \(X\), results in the team \(X_{\backslash v}\) obtained by removing the variable \(v\) (if present) from all assignments \(s \in X\) (and then, since \(X\) is a set, by collapsing identical assignments). This could be understood as a forgetting operation, through which we delete all information about the value of \(v\)—for example, because what we believed about this value was unreliable, or because this value has been altered. Now suppose that \(X_{\backslash v} = Y_{\backslash v}\): then, in our interpretation, this means that the sets of possible states of things represented by \(X\) and \(Y\) disagree at most with respect to the value of \(v\). Thus, if \(Y\) satisfies the condition \(\phi\), we may say that \(X\) would satisfy \(\phi\) if not for the value of \(y\), or, equivalently, that \(X\) satisfies \(\exists v \psi\). This justifies the following rule: