Explores a central thread unifying Russell's thoughts on logic in two works considered at odds with each other: "Principles of Mathematics" and "Principia Mathematica". The thread states that logic is an absolutely general science and any calculus for it must embrace unrestricted variables.

This book explores an important central thread that unifies Russell's thoughts on logic in two works previously considered at odds with each other, the Principles of Mathematics and the later Principia Mathematica. This thread is Russell's doctrine that logic is an absolutely general science and that any calculus for it must embrace wholly unrestricted variables. The heart of Landini's book is a careful analysis of Russell's largely unpublished "substitutional" theory. On Landini's showing, the substitutional theory reveals the unity of Russell's philosophy of logic and offers new avenues for a genuine solution of the paradoxes plaguing Logicism.

Landini's work is a significant contribution to Russell scholarship. It reveals with clarity the fecundity and coherence of Russell's early work in logic.