Synthesized answer
The provided passages do not contain information about the specific evidence the author provides in "Einführung in das mathematische Denken." [168] The passages only offer the title and page number of the book. Therefore, it is not possible to answer the question about the author's evidence based on the given material.
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