Cass Sunstein's Laws of Fear, published in 2005, is an influential attack on the precautionary principle (PP). Sunstein argues that, applied consistently, the PP leads to incoherent, paralyzing policy outcomes, unlike Cost-Benefit Analysis (CBA). According to Sunstein, the apparent appeal of the PP results from the influence of pervasive cognitive bias which causes people to selectively overlook possible outcomes. But if pervasive cognitive bias causes us to selectively overlook possible outcomes, so that we fail to realize that the PP would lead to policy paralysis if it were applied consistently, then it will also enable the PP to be applied by us biased reasoners without causing paralysis. A further problem for Sunstein is that if cognitive bias is pervasive then it undermines our applications of CBA. To establish that we biased reasoners should prefer CBA to the PP, Sunstein would need to demonstrate that the actual policy outcomes that the PP leads to, when applied by biased cognizers, are inferior to those that are recommended by the CBA. No such demonstration is made in Laws of Fear, so his overall argument is incomplete. I consider four ways in which Sunstein might try to quickly rejig his conceptual argument against the PP to address this problem and I argue that none would succeed. However, I argue that a 'slow' argument against the PP, which draws on empirical evidence about the possibility of ameliorating bias, alongside conceptual considerations, has good prospects of success.