Since electronic and open environments became a reality, computational trust and reputation models have attracted increasing interest in the field of multi-agent systems (MAS). Some of them are based on cognitive theories of reputation that require cognitive agents to display all their potential. One of them is Repage, a computational system based on a cognitive theory of reputation that focuses on the study of two important concepts: Image and Reputation. The possible integration of these Repage predicates into a cognitive agent architecture, like the well-known Belief, Desire, Intention (BDI) approach implies the definition of these two concepts as mental states, as a set of beliefs. In this paper, we specify a belief logic that captures the necessary elements to express Image and Reputation and we study their interplay by analyzing a classical definition of trust on information sources.