That comes as an explanation of the previous statements:

"Good God," I said to myself, "and this is merely New York! What must Mexico be like!" I supposed that I was experiencing normal conditions, whereas in point of fact I had landed at the climax of a heat wave which killed about a hundred people a day while it lasted. I should have discovered the truth if I had looked at a newspaper; but I did not read them.

In any case, that principle means we should probably refrain from reading HN too.

Interesting quote coming from him

I heard a very interesting talk on Crowley by Robert Anton Wilson once. Crowley did have some rather far-out ideas. Also, I seem to recall him being in cahoots with the British Intelligence services at the time.

https://www.youtube.com/watch?v=Qt8TZ0hYHiE