Why do design arguments—particularly those emphasizing machine metaphors such as “Organisms and/or their parts are machines”—continue to be so convincing to so many people after they have been repeatedly refuted? In this essay I review various interpretations and refutations of design arguments and make a distinction between rationally refuting such arguments (RefutingR) and rendering them psychologically unconvincing (RefutingP). Expanding on this distinction, I provide support from recent work on the cognitive power of metaphors and developmental psychological work indicating a basic human propensity toward attributing agency to natural events, to show that design arguments “make sense”unless one is cued to look more closely. As with visual illusions, such as the Müller-Lyer arrow illusion, there is nothing wrong with a believer's cognitive apparatus any more than with their visual apparatus when they judge the lines in the illusion to be of unequal length. It takes training or a dissonance between design beliefs and other beliefs or experiences to play the role that a ruler does in the visual case. Unless people are cued to “look again” at what initially makes perfect sense, they are not inclined to apply more sophisticated evaluative procedures.