sequent calculus

We discuss briefly the central ideas of linear logic, where by default assumptions must be used exactly once. 

Cut elimination for sequent calculus is more involved that normalization of detours for natural deduction.  There are more cases of cuts that must be transformed than correspond to detours (introductions followed by eliminations).  In this episode, I explain why that is.

We saw in the last few episodes that proofs in natural deduction can be simplified by removing detours, which occur when an introduction inference is immediately followed by an elimination inference on the introduced formula.  What corresponds to this for sequent calculus proofs?  The answer is cut elimination.  This episode describes the cut rule and what is meant by a cut-elimination procedure.  We will talk more about such a procedure in the next episode.