 If \(\phi_1\strictif\psi\) is true, then the shaded blue region is empty, and the position of \(\phi_2\) reflects the fact that \({\llbracket}\phi_2{\rrbracket}^R_v\subseteq{\llbracket}\phi_1{\rrbracket}^R_v\)—recall that all worlds above the x-axis are \(\phi_1\)-worlds. Since the shaded blue region within \(\phi_2\) is also empty, all \(\phi_2\) worlds in \(R(w)\) are \(\psi\)-worlds. That is, \(\phi_2\strictif \psi\) is true.