But Farmer's retelling of this pivotal historical event quickly reveals a number of differences, such as the presence of a friar of the Rogerian order aboard the Santa Maria, communicating with his counterpart at Las Palmas by means of a "cherubim realizer" -- a kind of radio operating according to principles quite unlike those of our world. Thus, it's clear that "Sail On! Sail On!" takes place in an alternate reality, a fact Farmer himself brings to the reader's attention when the friar discusses this very topic with two sailors aboard ship:
“This Father Sparks on the Grand Canary is so entertaining. He stimulates me with all sorts of philosophical notions, both valid and fantastic. For instance, tonight, just before we were cut off by that”—he gestured at the huge bloodshot eye in the sky—“he was discussing what he called worlds of parallel time tracks, an idea originated by Dysphagius of Gotham. It’s his idea there may be other worlds in coincident but not contacting universes, that God, being infinite and of unlimited creative talent and ability, the Master Alchemist, in other words, has possibly— perhaps necessarily—created a plurality of continua in which every probable event has happened.”As you can see, the world Farmer presents us is one where medieval scientific notions are fact rather than mere conjecture and, thanks to men like Roger Bacon -- St. Roger, as he's called here -- technology has developed to utilize those notions to create wondrous new devices, like the aforementioned cherubim realizer radio. It's a very imaginative conceit that only highlights the difficulty in distinguishing between fantasy and science fiction in many cases. Some might be inclined to call any story where objects fall at different velocities according to their weights a work of fantasy, but others might reasonably point out that, while it's true that the setting "Sail On! Sail On!" operates according to different physical laws than our own, Farmer exactingly applies those laws in a fashion that's probably a good deal more rigorous than SF staples like faster-than-light travel.
“Huh?” grunted de Salcedo.
“Exactly. Thus, Columbus was turned down by Queen Isabella, so this attempt to reach the Indies across the Atlantic was never made. So we could not now be standing here plunging ever deeper into Oceanus in our three cockle-shells, there would be no booster buoys strung out between us and the Canaries, and Father Sparks at Las Palmas and I on the Santa Maria would not be carrying on our fascinating conversations across the ether.
“Or, say, Roger Bacon was persecuted by the Church, instead of being encouraged and giving rise to the order whose inventions have done so much to insure the monopoly of the Church on alchemy and its divinely inspired guidance of that formerly pagan and hellish practice.”
De Torres opened his mouth, but the priest silenced him with a magnificent and imperious gesture and continued.
“Or, even more ridiculous, but thought-provoking, he speculated just this evening on universes with different physical laws. One, in particular, I thought very droll. As you probably don’t know, Angelo Angelei has proved, by dropping objects from the Leaning Tower of Pisa, that different weights fall at different speeds. My delightful colleague on the Grand Canary is writing a satire which takes place in a universe where Aristotle is made out to be a liar, where all things drop with equal velocities, no matter what their size. Silly stuff, but it helps to pass the time. We keep the ether busy with our little angels."
Of course, this being a Philip José Farmer short story, "Sail On! Sail On!" contains elements of satire too, both of medieval and modern thinking about science and the faith we place in it. What makes this short story so enjoyable is that, just as the reader has acclimated himself to the Scholastic scientific worldview that underlies it, Farmer reveals that he has another trick up his sleeve and calls into question everything we'd just come to accept. I really enjoyed this short story when I first read it years ago and I think I enjoy it even more now. I appreciate fiction where pre-modern people are shown as something other than superstitious buffoons, just as I appreciate fiction that calls into question our own surety that we are any more knowledgeable about reality than they. "Sail On! Sail On!" is great fun; if you can find a copy of it, you won't regret reading it.