Fuente TeX:

\begin{array}{l l}\bar{\forall} a \in \vert \mathcal{M} \vert . \mathcal{M}  \models (P(\bar{a}) \to (\exists z)(P(z)) & ( \text{ por 2.4.5 para } \forall ) \\\text{Por esto, tomando un } a \text{ arbitrario de } \vert \mathcal{M} \vert \text{se cumple que: } \\ \mathcal{M}  \models (P(\bar{a}) \to (\exists z)(P(z))) \\  \mathcal{M}  \models P(\bar{a}) \Rightarrow  \mathcal{M}  \models  (\exists z)(P(z)) & \text{Por 2.4.5 para } \to \\\end{array}