"Yes, though it's not so simple as making someone watch the cartridge. The ability stems from something we call 'the touch', which all Gunslingers have varying levels of contact with. Hypnosis is one of the few ways we can actually directly control it. It's not quite the same as magic, though I once encountered a witch who used it to implant commands in people's minds, to quite destructive ends. It takes years of mastery, though. When my friends and I were taught as boys, we'd hypnotize each other under the watch of one of our instructors, Cort or Vanaay. If you're inexperienced, it's very easy to accidentally kill the person, or put them into a coma."