The idea of lean deduction is to achieve maximal efficiency from minim
al means. Every possible effort is made to eliminate overhead. Logic p
rogramming languages provide an ideal tool for implementing lean deduc
tion as they offer a level of abstraction that is close to the needs f
or building first-order deduction systems. In this paper, we describe
the principle of lean deduction and present leanT(A)P, an instance of
it implemented in standard Prolog.