Synthesized answer
The provided passages do not contain enough information to answer the question about explaining the key concepts of "Principia Metaphysica (with Bernard Linsky)" in my own words. The passages only include the title of a different work, "Procedures and Metaphysics by Edward William Strong," and its category, "Mathematics." There is no content from "Principia Metaphysica (with Bernard Linsky)" available to draw upon.
Synthesized from the book passages below. Chat with the book on Feynman for follow-up.
From the book
Title: Procedures and Metaphysics by Edward William Strong Categories: Mathematics