 Theorem 3. Consider a valid argument \((\Gamma,\phi)\), and assume that the premise set \(\Gamma\) is consistent, and that every premise \(\gamma\in\Gamma\) is relevant (i.e. \(\Gamma-\{\gamma\}\not\models\phi\)). Then there exists a probability function \(P:\mathcal{L}\to[0,1]\) such that