Timothy Williamson has argued that the safety condition on knowledge places certain limits on iterations of knowledge. But at the same time, Williamson claims that interpersonal iterations of knowledge aren’t so restricted as to rule out ordinary cases. The present authors show that Williamson’s discussion misconstrues the challenge to iterated interpersonal knowledge. The proper argument against interpersonal iterations is rather what the authors call a third-person argument that does not share the major weaknesses of the argument Williamson considers. The challenge (...) that the safety condition poses to interpersonal iterations of knowledge therefore seems robust, even in ordinary cases. But the authors also identify an underlying assumption that their argument relies on, and they show that Williamson’s original argument as well as his argument against intrapersonal iterations of knowledge rely on analogous assumptions. In assessing the extent of the clash between safety and iterated knowledge, the focus must be on the viability of these assumptions. (shrink)