Esotericism and mysticism are two notoriously elusive concepts. Both are based on referential corpora of works that are so internally diverse as to defy any simple characterization. A definition of mysticism needs to encompass a range of empirical cases that include medieval Christian visionaries, Sufis, and Hindu gurus such as Ramakrishna. Similarly, the term esotericism denotes the work of individuals as diverse as Paracelsus, Swedenborg, and Carl Gustav Jung. Unsurprisingly, in a recent encyclopedia article (Nelstrop 2016) mysticism has been characterized as a ‘taxonomical black hole’, while esotericism has been described by a leading scholar on that topic, Wouter J. Hanegraaff (2005, 2012), as a waste-basket category for a range of currents that have little else in common than having been rejected by mainstream theologians and by rationalists from the Enlightenment to our own time. This article argues that the terms are not only laden with significant definitional problems, but that applying them to any particular phenomenon has little, if any, theoretical added value. Instead, this article advocates a higher-level taxonomy that sees the elements of both sets as examples of a more general category: religious phenomena which are supported by charismatic authority.