Tashiro, MasayukiThis dissertation consists of three standalone papers centered around the concept of unawareness. The first paper, titled `Weak Explicit Beliefs', concerns the effect of unawareness to one's beliefs and extends the standard logic framework of awareness with a novel notion of beliefs under unawareness. The second paper, titled `Learning under Unawareness' concerns the effect of unawareness in one's learning process and extends the standard logic framework of awareness with two dynamic modal operators: learning and change of awareness. Lastly, the third paper, titled `Models of Group Deliberation with Asymmetric Awareness' concerns the effect of unawareness in group decision making situations, in which each agent in the group may be un/aware of different things, and explores a normative question whether it is always better to become more aware (of what the other agents in the group are aware of) via two formal models of group deliberation.enDissertationLogicPhilosophyEconomicsAwarenessGroup Decision MakingImplicit/Explicit BeliefsPublic Announcement Logic