'On Certainty' and Formal Epistemology Moritz Bäumel Abstract: We look at Wittgenstein’s epistemological work On Certainty from the point of view of formal epistemology. Different interpretations of the work are looked at and important aspects of them are worked out. We take probability theory as a basis and interpret probabilities in terms of betting quotients, i.e. as a basis for action, and define certitude as probability 1. On top of this we define such notions as belief, doubt and knowledge in the spirit of On Certainty, following work done by A. Baltag. We proceed by looking at ways of (i) extending this system to a multi-agent system, (ii) outfitting it with an internal perspective and (iii) dynamics. We also look at game-theoretic approaches. The merits of the work will be discussed, as well as shortcomings and future work to be done.