The ‘knowledge argument’ is one of the most controversial attacks to physicalism in the literature. In a strong version the argument tries to establish that conscious expe-rience involves non-physical facts. Jackson’s formulation of the argument through the well-known thought experiment of Mary has led to the emergence of a wide range of defenses of physicalism. Our main interest in this paper is to evaluate one of the defenses the physicalist thesis has received against the knowledge argument in Jackson’s version. The chosen response has the advantage not only of showing an alleged fallacy in the argument of Jackson, but of presenting an explanation of why this argument is so compelling at first glance. The essential point to be addressed in this physicalist response is to recognize that conscious experience of something and its scientific description are two different forms of epistemic access to the same fact. But this does not tantamount to knowledge of new facts that remain ignored in the physicalist perspective, but just another way to look at the same events described in physicalistic terms. Firstly a reconstruction of Jackson’s argument will be presented, then briefly discussing the main responses offered against Jackson’s argument. Secondly, we present the thesis of concept dualism. Finally we outline some of the main problems concept dualism problems has to face and possible solutions to them.