It is widely held that assertions are partially governed by an epistemic norm. But what is the epistemic condition set out in the norm? Is it knowledge, truth, belief, or something else? In this paper, I defend a view similar to that of Stanley (2008), according to which the relevant epistemic condition is epistemic certainty, where epistemic certainty (but not knowledge) is context-sensitive. I start by distinguishing epistemic certainty, subjective certainty, and knowledge. Then, I explain why it's much more plausible (...) to think that "certain", rather than "know", is context-sensitive. After that, I respond to an important worry raised by Pritchard, according to which the proposed view is too strong to accommodate our current practice of assertion. I then show that the main linguistic and conversational data advanced in the recent literature in favour of the knowledge condition are best explained by the certainty view. Finally, I offer two principled considerations: the certainty view is the only one compatible with three independently plausible claims and it fits very well with the common thought that knowledge does not entail certainty. (shrink)