In Language, epistemology, and mysticism, Steven T. Katz presents his theory of the interpretation of mystical experience reports in which the foundational epistemological claim is that there are no pure experiences. Around this claim, he developes a theory of interpretation that implies the rejection of a common core in mystical experience. This theory also involves a criticism against the so called perennial interpretations of mystical experience and of the phenomenal characteristics that are considered to be prevalent in mystical experiences across traditional religious boundaries. Katz’s theory has been interpreted and criticised as a ‘constructivist’ theory of meaning, implying cognitive relativism and non-realism for the experiences of mystics. As a theory of interpretation, purporting to be superior to the perennial models of interpretation, Katz’s theory is evaluated in terms of their scientific value for the interpretation of mystical reports.