That if Blinky were ever caught, there would also turn out to be no Æther.
* * * * * * * * * *
Being that I'm writing this in 2025, I can say that Merle was correct. Blinky was caught (and hanged) and there was no Æther. Now, that doesn't mean he was correct that these two events were somehow entangled. But was he?
Within the reality of Pynchon's novel, Æther currently exists. Reality actually changes as scientists discover more and more secrets of the physical universe. There's an almost magical realist air to the book, as in Mason & Dixon. I don't know if this is a general theme in Pynchon's work or not. Gravity's Rainbow feels like it's more grounded and the weird, fantastical bits all make sense in the perception of the characters or simply Pynchon's use of other medium through his text (like scenes devolving into musicals or spinning newspapers to shout headlines or comic books). But Gravity's Rainbow also deals quite a bit with the investigation of the supernatural so maybe? One thing I'm really noticing on my current re-read of Gravity's Rainbow (as well as Mason & Dixon. Don't forget that book!) is how much he alludes to predestination (the Elect vs the Preterite, in particular) versus free will.
But back to this sentence, Merle sees these two events as entangled so perhaps they are? Perhaps Merle's belief actually destroys Æther when Blinky Morgan is captured and hanged. The experiment itself doesn't prove the existence of Ætheric drift which begins the decline in people's belief in it. But what if that wasn't what killed it? What if Merle did?
