Abstract: Suppose I intend to give up smoking, having never tried to quit before. I know that 95 per cent of smokers fail to give up on the first attempt. Nonetheless, I promise my partner: I will give up on the first attempt. Here, I promise against the evidence. Such promises are puzzling. On the one hand, it seems that such promises can be licit. On the other, it seems that they must either be insincere or reckless. I consider various extant responses to the puzzle. They are inadequate: they cannot account for the capacity of such promises to yield knowledge in the promisee.