Hi Daniel, it’s from, I think, the analysis of the consequences of discovering the cosmic microwave background. One of the concepts ancient philosophers discussed was the notion of boundary or limit. Think the logic of the limited and the unlimited. The CMB presents the idea that our universe is limited. Well if so , the logic of the limited /unlimited requires us to consider the question: what is outside of the limit of the CMB?

There are at least two answers to this question logically - something or nothing.

Hawking is considering ‘something’ in this article. And how to possibly find that something.

This is speculative stuff, no doubt, but it is speculation fully within the logic of contemporary scientific thinking. IMO, of course.