This dissertation concerns the location and nature of phenomenal qualities. Arguably, these qualities naively seem to belong to perceived external objects. However, we also seem to experience phenomenal qualities in hallucinations, and in hallucinations we do not perceive any external objects. I present and argue for a theory of the phenomenal qualities, "brain theory", which claims that all phenomenal qualities we experience are physical properties instantiated in the brain, regardless of whether they are experienced in veridical perceptions or in hallucinations. I begin by more carefully identifying the phenomenal qualities, discussing how they are related to "qualia" and "phenomenal character". Then I present brain theory, and investigate its implications for the perceptual relations we stand in to external objects, noting that it is mostly neutral. I also compare brain theory to a similar theory of perception advocated by Bertrand Russell. Next, I provide an overview over the competing theories of phenomenal qualities, and relate them to theories of perception, such as representationalism, qualia theory, sense data theory and disjunctivism. The majority of my argumentation for brain theory focuses on arguing that the phenomenal qualities are instantiated in the brain, rather than on arguing that they are physical properties. Instead, I largely assume physicalism. However, even independently of the physicalism assumption, I show that we have reason to believe that phenomenal qualities are experienced in hallucinations, and that qualities experienced in hallucinations are instantiated in internal objects, such as our brains or sense data. In the first step towards this conclusion I argue that theories which deny that phenomenal qualities are experienced in hallucinations face serious problems. In the next step I argue that theories which deny that phenomenal qualities experienced in hallucinations are instantiated in internal objects face serious problems. Finally, an important part of the argumentation is my replies to objections against brain theory, including common sense objections and the "observation objection". From these conclusions, together with the physicalism assumption, I infer that we have reason to believe that brain theory is true about hallucinations. On this basis, I then argue, through a generalizing argument, that the same is the case for veridical perceptions.