Kant's characterization of noumena as the phenomena of the immaterial realm is helpful. Both are 'in themselves' unknowable, but make impressions on our consciousness of which we can and do become aware. Both are thereby sources of information. Sufficiently verified information is what knowledge is. Beliefs, from noumena, are a form of knowledge, but we make them true when we accept them. Information from material phenomena gains validity through repetition/predictability and confirmation by other people. At least, that’s my understanding.