What is attention? Attention is often seen as a subject matter for the hard sciences of cognitive and brain processes, and is understood in terms of sub-personal mechanisms and processes. Correspondingly, there still is a stark contrast between the central role attention plays for the empirical investigation of the mind in psychology and the neurosciences, and its relative neglect in philosophy. Yet, over the past years, several philosophers have challenged the standard conception. A number of questions concerning the nature of attention arise. This article provides an introduction to contemporary debates concerning these questions. In particular, it discusses the question of how the pre-theoretic conception of attention might be reconciled with a scientific conception, arguments that provide support for an anti-reductionist theory of attention, and sketches several recent anti-reductionist theories and their inter-relations.