Based on the 2 × 2 matrix of current theories of self-consciousness developed in chapter " A Brief Overview of Philosophy of Self-Consciousness", this chapter presents key challenges in the current, widespread philosophy of self-consciousness. Its perspective is inspired by the work of the Heidelberg School of self-consciousness (Dieter Henrich, Manfred Frank, Ulrich Pothast, and Konrad Cramer). In a word, reflective theories struggle with infinite regress and vicious circularity, no matter if they are egological or non-egological. Rosenthal's higher-order theory serves as an example here, by putting it in contrast with Henrich's thinking. Furthermore, self-consciousness cannot simply be understood as propositional. Rödl's and Tugendhat's account are critically examined in this context, based on Frank's work. Current pre-reflective theories do not explain much about what self-consciousness actually is and thus suffer from what is here called the "ex negativo" challenge. Zahavi and Gallagher's account illustrates this issue. Non-egological theories, such as Kriegel's self-representationalism have problems to account for the unity of the phenomenon. Peacocke's recent proposal is discussed in this context, too.