Synthesized answer
The provided passages do not contain information that allows for an explanation of the key concepts in my own words. The passages only state the title, categories, and page count of "Mysticism and Logic" by Bertrand Russell [1]. There is no content within these passages that defines or describes any key concepts from the work. Therefore, I cannot answer how to explain the key concepts from the provided text.
Synthesized from the book passages below. Chat with the book on Feynman for follow-up.
From the book
Title: Mysticism and Logic by Bertrand Russell Categories: Mathematics Pages: 256