Abstract

LK is much more difficult than NK, and to make matters worse, Gentzen's intention is still unclear when it comes to that system (LK). This book, Vol.1 of the series titled What is LK?, tackles this issue, focusing on the sequent, the most enigmatic notion we find in LK. The dependence-relation we find in NK shall play a crucial role in that investigation. The style is typically textbook-like, so readers can learn the system of LK, using this series as a guidance, too.