It sounded blatantly false, so I looked up the paper; and it seems Taleb might be saying that the road is not simply reversible and that one direction is not just the same as the other. I hope. Because, I mean, really, what do you call a nuclear weapon if not a practical application of theoretical knowledge? Fission weapons did not exist in nature before they were envisioned based on abstract knowledge (by Leo Szilard, in his bathtub).