Logic and Structure

from a Customer's Review: This book is an introductory treatment of mathematical logic, written entirely from the perspective of GENTZEN natural deduction. Standard texts are written from the viewpoint of Hilbert axiomatics or from (an alternative from Gentzen) natural deduction. Thus, for one wanting any discussion of the Gentzen calculus ND this book is the only full, start from scratch, treatment that I know of. Note, however, that the Gentzen sequent calculus is NOT discussed.