Proof of Proposition 4 for the Completeness Theorem

This is a proof of Proposition 4 in §17.2 of the textbook LPL.

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Notes for slide-4:

\subsection{slide-4}

We want to provide this slightly stronger claim (because we're going to do induction)

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Notes for slide-7:

\subsection{slide-7}

We know that Y cannot be a sentence letter or its negation from the assumption about how h() was defined

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Notes for slide-3:

\subsection{slide-3}

Let's consider a case.

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This is a proof of Proposition 4 in §17.2 of the textbook LPL.

Define a structure, h, so that:

h(P)=T when P is in A*

h(P)=F when ¬P is in A*

Claim: h(X)=T for every X such that A* ⊢ X

Let's consider a case.

15.33--15.40 (second edition)

15.33, 15.37--15.39 (second edition)