for which those experiences offer the prove. In this approach, mystical experiences are privatised, separated from the context in which they emerge. William James, in his The Varieties of Religious Experience, was highly influential in further popularising this perennial approach and the notion of personal experience as a validation of religious truths. The essentialist model argues that mystical experience is independent of the sociocultural, historical and religious context in which it occurs, and regards all mystical experience in its essence to be the same. According to this "common core-thesis", different descriptions can mask quite similar if not identical experiences: Principal exponents of the perennialist position were William James, Walter Terence Stace, who distinguishes extroverted and introverted mysticism, in response to R. C. Zaehner's distinction between theistic and monistic mysticism; Huston Smith; and Ralph W. Hood, who conducted empirical research using the "Mysticism Scale", which is based on Stace's model. Since the 1960s, social constructionism argued that mystical experiences are "a family of similar experiences that includes many different kinds, as represented by the many kinds of religious and secular mystical reports". The constructionist states that mystical experiences are fully constructed by the ideas, symbols and practices that mystics are familiar with, shaped by the concepts "which the mystic brings to, and which shape, his experience". What is being experienced is being determined by the expectations and the conceptual background of the mystic. Critics of the "common-core thesis" argue that The principal exponent of the constructionist position is Steven T. Katz, who, in a series of publications, has made a highly influential and compelling case for the constructionist approach. The perennial position is "largely dismissed by scholars", but "has lost none of its popularity". The contextual approach has become the common approach, and takes into account the historical and cultural context of mystical experiences. Steven Katz – constructionism After Walter Stace's seminal book in 1960, the general philosophy of mysticism received little attention. But in the 1970s the issue of a universal "perennialism" versus each mystical experience being was reignited by Steven Katz. In an often-cited quote he states: According to Katz (1978), Stace typology is "too reductive and inflexible," reducing the complexities and varieties of mystical experience into "improper categories." According to Katz, Stace does not notice the difference between experience and interpretation, but fails to notice the epistemological issues involved in recognizing such experiences as "mystical," and the even