Logically self-contained, which just means that the treatment doesn’t assume outside knowledge. Difficulty level is not bounded from above.
Beginner-friendly, which means the presentation is tailored to people without a strong background in the subject.
Penrose falls squarely in Category 1. An intelligent reader can probably push the definitions around enough to follow the presentation, but that’s not the same as understanding what’s actually going on.
There are two categories of “self-contained”:
Logically self-contained, which just means that the treatment doesn’t assume outside knowledge. Difficulty level is not bounded from above.
Beginner-friendly, which means the presentation is tailored to people without a strong background in the subject.
Penrose falls squarely in Category 1. An intelligent reader can probably push the definitions around enough to follow the presentation, but that’s not the same as understanding what’s actually going on.