!!MagicVersusScience as a theme in the series (or just the first game).
* MagicVersusScience: it is said in the second game that humans and elves are not indigenous of the world they live in but that during a convergence of spheres event humans arrived on metal ships and elves arrived on white ships (some non supernatural monsters apparently arrived in similar fashion hence why they have no real place in the ecosystem) hinting at the fact that, while magic exists in this universe, there are some remnants of a higher tech left behind. Coincidentally, Witchers are mutants, genetically mutated humans to be precise (notice the double Helix symbol in the mutagens menu and the distinctly cellular look of the mutagens themselves which some fans disliked for their sciencey look) created to deal with things normal humans could not (the supernatural) and a lot of well read individuals in the game know an awful lot about mutations and evolution. Sounds like the Witchers might be the earliest attempt of the newly arrived humans to fight back the hostile, unknowable forces of this universe using their own technology.