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 The heart of Landini's book is a careful analysis of Russell's largely unpublished "substitutional" theory.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.

The author provides deep insights into a very dynamic period of Russell's tackling with logical systems by stressing the unifying role of the substitutional theory. * V.Peckhaus, MATH, Vol.933 *
Landini's book ... supplies a valuable and convincing picture of how Russell hoped the theory of incomplete symbols might show the way to a philosophically defensible solution to the paradoxes. * Michael Byrd, Brit. Jnl. Phil Sci. 51, No.2 (2000). *
the detailed elaboration of the substitutional theory in the book's second part is quite impressive. * Michael Byrd, Brit. Jnl. Phil. Sci. 51, No.2 (2000). *
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. * Michael Byrd, Brit. Jnl. Phil. Sci. 51, No.2 (2000). *