Spreading Change: Diffusional Change in the English System of Complementation examines the emergence and spread of three types of complements from the Middle English period to the present day. The three types of complements are subject-controlled gerund complements (1), for...to-infinitives (2), and subject-controlled participial compelements (3).

(1) The cat loves being stroked, absolutely loves it!
(2) We couldn't afford for it to go wrong.
(3) The receptionist is busy filling a fifth box.

In the first half of the book De Smet addresses the theoretical issues by summarizing a number of major approaches to the study of complementation, and by focusing on how and why a particular change spreads (a process that he calls "diffusion"). In the second half, which is descriptive and largely corpus-based, De Smet tests these mechanisms on the three complement types. His work demonstrates: a) how diffusion interacts with the grammatical system of complementation; b) how diffusion proceeds, step-by-step; and c) why diffusion is directional.