The subject matter of this thesis is Frank Jackson´s knowledge argument, a famous example of a thought experiment that aims at disproving the basic contention of physicalism that everything that exists is physical in nature. It is claimed that physicalism cannot accommodate the existence of qualia, the intrinsic properties of experiences such as the visual experience of colors. There are different responses to this challenge, some dualist, others physicalist in nature, and the main task of this paper is to explore in detail two physicalist theories or solutions to the problem of the knowledge argument; first Dennett´s eliminativist, and then Perry´s antireductionist strategy, and by keeping in mind the basic distinction between conceptual and logical – semantical levels of discussion. Dennett is denying the existence of qualia in every sense of the term, so he is trying to eliminate both the use of phenomenal concepts and phenomenal content from every kind of meaningful philosophical discourse. Perry is advancing the opposite idea, claiming that phenomenal experiences and their qualia are real and that first-person beliefs about them should be analyzed in terms of demonstrative / recognitional concepts and reflexive content. After comparing Dennett´s and Perry´s ideas on the matter, I conclude that Perry´s proposal is more plausible, primarily because eliminativism cannot explain the possibility of there being different ways of thinking or representing qualia or subjective qualities of experience (from the first person, and the third person perspective).