Soundness of deductions from premises 「 Theorem If there is a tableau proof of a from a set of premises 2 then a is a consequence of∑,ie.∑}a→∑haSoundness of deductions from premises Theorem If there is a tableau proof of α from a set of premises Σ, then α is a consequence of Σ, i.e. Σ ` α ⇒ Σ  α. Yi Li (Fudan University) Discrete Mathematics April 24, 2012 9 / 25