Tableau proof Definition a tableau proof of a proposition a from 2 is a tableau from 2 with root entry Fa that is contradictory, that is one in which every path is contradictory. If there is such a proof we say that a is provable from 2 and write it as ∑卜aTableau proof Definition A tableau proof of a proposition α from Σ is a tableau from Σ with root entry Fα that is contradictory, that is, one in which every path is contradictory. If there is such a proof we say that α is provable from Σ and write it as Σ ` α. Yi Li (Fudan University) Discrete Mathematics April 24, 2012 7 / 25