In the “Knowledge Argument” also proposed by Frank Jackson, known as Mary's room, in his article entitled Epiphenomenal Qualia, Jackson opposes physicalism and the view according to which universe, including everything conscious/mental is completely physical. Although Jackson no longer agrees with it, it is still known as one of the most significant arguments in the philosophy of mind. In this article I will explain the argument, evaluate its validity and soundness, explain what problem it presents for physicalism, the basic structure of Lewis's response, and whether Lewis's response is convincing. The Knowledge Argument is deemed valid. If an argument is valid then it means that the structure guarantees that, if the premises are true, the conclusion must also be true. The Knowledge Argument is invalid because if it were then it would mean that physicalism is false; but physicalism is not false, so the Knowledge Argument is valid. I believe that physicalism is true and that everything that could/exists is physical or depends on the physical. Since I believe the knowledge argument states that physicalism is true, the argument is valid. The Knowledge Argument can simply be defined as one who can know all the objective and physical facts about conscious experiences, but does not yet fully know human conscious experiences, so physicalism is false. Frank Jackson has two cases involving physicalism: the Mary case and the Fred case. The Fred Case is a case where a man named Fred sees two colors; his consciousness developed the use of the two words red and red. “In any case he explains to us that it would be completely wrong to think that, since 'red' appears in both 'red (1)' and 'red (2)', the two colors are shades of... . middle of the paper ......Mary's change after leaving the room in black and white. The ability hypothesis simply states that knowing what an experience is like is the same thing as knowing how to imagine having an experience. I agree with Lewis because there are no facts to support how to perform a certain action because you have to actually experience something yourself to know how to do something. In conclusion, the Knowledge Argument proves to be a valid argument, but not a sound one. I explained all the premises that accompanied the Knowledge Argument and what problem physicalism affects. I also examined and showed Lewis's response to the Knowledge Argument and whether Lewis's is convincing or not. Overall, I believe that almost everything in this universe is physical. The Knowledge Argument will always be known as one of the most significant topics in the philosophy of mind.