That’s not his point at all!

His point emphasized the limitations of science – scientists can’t know about things that can’t be observed. Scientists of the very distant future would never support a theory of the universe that suggested there was more than one galaxy. They wouldn’t support such a theory because they would have no evidence to suggest it as a possibility. Their theories of the universe would all be consistent with a single galaxy existing in an immeasurably large void.

And his concluding point was this: They would be wrong.