I defend Frank Jackson’s knowledge argument against the a priori physicalist objection that for all we know, the deducibility thesis, the thesis that phenomenal knowledge is in principle deducible from physical/functional knowledge, is true. I discuss the force of the common intuition against the deducibility thesis and the plausibility of the attempts in the literature in defense of the deducibility thesis. I argue that a priori physicalists both fail to remove the burden of proof from their shoulders to convince us that deducibility thesis is plausible and fail to offer an intelligible scenario in which phenomenal knowledge is possibly deduced from physical/phenomenal knowledge.