Synthesized answer
The provided passages are insufficient to explain the key concepts of "Einführung in das mathematische Denken" in my own words. The passages only contain the title, author, and page number [168]. There is no content from the book itself that discusses any concepts, let alone key ones.
Therefore, I cannot provide an explanation of the key concepts as requested, nor can I ground any claims in the passages or cite specific chapters, as the necessary information is absent.
Synthesized from the book passages below. Chat with the book on Feynman for follow-up.
From the book
Title: Einführung in das mathematische Denken : Die Begriffsbildung der modernen Mathematik by Friedrich Waismann, Karl Menger Pages: 168