\subsubsection{For $L \nothaspatch \p, R \nothaspatch \p$:}
$D \not\isin L \land D \not\isin R$. $C \not\in \py$ (otherwise $L
-\in \py$ ie $\neg[ L \nothaspatch \p ]$ by Tip Own Contents for $L$).
+\in \py$ ie $L \haspatch \p$ by Tip Own Contents for $L$).
So $D \neq C$.
Applying $\merge$ gives $D \not\isin C$ i.e. $C \nothaspatch \p$.
various cases that
if $M \haspatch \p$, $D \not\isin C$,
whereas if $M \nothaspatch \p$, $D \isin C \equiv \land D \le C$.
+And by $Y \haspatch \p$, $\exists_{F \in \py} F \le Y$ and this
+$F \le C$ so this suffices.
Consider $D = C$: Thus $C \in \py, L \in \py$.
By Tip Own Contents, $\neg[ L \nothaspatch \p ]$ so $L \neq X$,