The philosophical literature on self-knowledge has up to now paid too little attention to emotional phenomena. Part of the reason for this is that the philosophy of self-knowledge tends to focus on cases of so-called trivial self-knowledge. This volume focuses instead on “substantial” self-knowledge, which is both difficult to get and personally valuable for its subject. As this volume shows, affective states play a crucial role in acquiring substantial self-knowledge. This introduction distinguishes three main kinds of affective states: emotions, moods, and sentiments. It claims that, due to their evaluative character, these phenomena can give us access to what we care about and value, and thereby they can help us obtain knowledge of fundamental aspects of our person like, e.g., our character traits. Finally, the introduction gives an overview of the different chapters in the volume and the main threads that run through it, including what affective states illuminate and what they obstruct about us, which sorts of spaces for self-knowledge they provide, how do they affect the dynamic formation of our self-concepts and self-narratives, through which mechanisms they foster or hinder self-knowledge and which roles do other people play in emotional self-knowledge.