This paper argues for a new epistemic condition for machine mentality: we are only justified to attribute mentality to systems whose internal workings we cannot fully understand. I call this the mechanistic opacity condition. Methodologically, I argue that machine consciousness studies should be continuous with other minds studies. With an inference to the best explanation argument, I argue that a mechanistic explanation that is better than a mental explanation always exists for a mechanistically transparent system, thus rendering consciousness attribution to them unjustified. Despite behavioral similarities to humans, current AI systems cannot be considered conscious, intelligent, intentional, or mental in important ways, simply because we understand how they work. This condition explains intuitions about classic thought experiments (China Brain, Blockhead, Chinese Room) and provides principled AI consciousness skepticism without biological chauvinism.