Definition:Sound Proof System

Definition
Let $\LL$ be a logical language.

Let $\mathscr P$ be a proof system for $\LL$, and let $\mathscr M$ be a formal semantics for $\LL$.

Then $\mathscr P$ is said to be sound for $\mathscr M$ :


 * Every $\mathscr P$-theorem is an $\mathscr M$-tautology.

Symbolically, this can be expressed as the statement that, for every logical formula $\phi$ of $\LL$:


 * $\vdash_{\mathscr P} \phi$ implies $\models_{\mathscr M} \phi$

Also known as
Many sources obfuscate the distinction between sound and strongly sound.

Some sources speak of consistent proof systems. However, on, consistency is a term only applied to (sets of) formulas.

Also see

 * Definition:Complete Proof System