\doc{Proofs by specialization}
\ref{proof-by-specialization}
\ref{specialization}
\ref{specialize}
\ref{specializing}

The command \fq{prove F by specializing x to t} directs LP to prove a formula
\fq{F} by creating a single subgoal in which all
\glink{accessible}{accessible} 
\glink{prenex}{prenex-existential} quantifiers over the variable 
\fq{x} have been eliminated from \fq{F} and all occurrences of \fq{x} bound by 
those quantifier have been replaced by \fq{t}.  
\p
The command \fq{resume by generalizing x from t} directs LP to resume the proof
of the current conjecture by this method.
\p
This proof method, which eliminates existential quantifiers from a conjecture,
is the dual of the \cflink{instantiate} command, which eliminates universal
quantifiers from facts.
\p
For example, the command
\begin{verbatim}
prove \A x \E y (x < y) by specializing y to s(x)
\end{verbatim}
reduces the proof of the conjecture to establishing the subgoal \fq{x < s(x)}.

