Some Thoughts on the Logic of Imprecise Observation Alexandru Baltag, Johan van Benthem Abstract: We propose a dynamic-epistemic analysis of perceptual knowledge placing structured observational events at center stage. Our starting point is the specific entanglement of epistemic accessibility with the relation of ‘closeness’ or similarity, that is claimed in the so-called Margin of Error principle. While we find the standard formulation of this principle to be defective, we think that it contains valuable intuitions for a joint logic of closeness and uncertainty, whose contours we develop. In particular, our analysis explains how imprecise observation can lead to higher-precision knowledge.