Well, there are a number of different qualities that that science fiction and fantasy share and do not share. One key similarity is, of course, the fact that things that are not possible in the real world are possible in the fictional one. The key difference between the two in this regard is that in fantasy, the past held arcane secrets and the powers of gods held sway; the world is in decline from this power and may someday be no more magical than our own. Science Fiction, on the other hand, promises that as time goes on, new secrets will be unlocked, and new miracles become possible. In science fiction, we look forward to ever more amazing powers.
Of course, there are reversals of both of these- Star Wars miiiight be called Sci-Fi, despite being heavily based on fantasy archetypes, and I'm sure that somewhere there is a dungeons and dragonesqe setting where magic is being reinvented- but the rules I've outlined above are generally true.
In the setting we're discussing here, we can reverse and combine both of these laws; On the one hand, the ancient technology hearkens back to a time when logic and reason shaped the world. On the other, Magic (or at least technology so advanced it is in all respects magical) is driving a Renaissance.
Talking to Tahin, we've been thinking that purely supernatural magic could be removed from the setting entirely; we could have all the magic in the game be advanced technology so long forgotten that it is inexplicable. I myself like the idea of making it entirely unclear. It MAY be that everything is explained by mystical forces, or it may be that everything is technology, or it may be both, with the interpretation entirely up to the player, be they sitting at a screen or a table.