This paper provides an analysis of the cognitive processes implied in the ego defense known as projection. Projection is first placed in the context of the general cognitive processes of attribution and ascription. Then we address defensive projection, and identify its distinctive features. In particular, whereas general projection consists in the ascription of one's own mental attitudes to others, defensive projection implies one's rejection (via denial or repression) of the ascribed mental states, and ascription is a means for supporting this rejection. We try to understand how and why ascription is functional to rejection. Then, we examine a few types of defensive projection, and identify the main components and steps in the projective process. Finally, we draw some general conclusions.