Owing to the characteristic of temporal logic,some rules of classical logic can't be used directly when doing temporal natural deduction. Though the N system shows us a solution of this problem in which all rules or deductions are divided into two types-verticality and horizontality, the two-dimensional mode also gives rise to some difficulties in deduction. This paper presents an NL system (a loose natural deduction system of temporal logic) that provides us with a unified view of all rules and deductions. In fact,we can prove as well that NL is equivalent to N and that for every N deduction ...
