The scholar of religion Paul Heelas characterised the New Age as "an eclectic hotch-potch of beliefs, practices, and ways of life" that can be identified as a singular phenomenon through their use of "the same (or very similar) "lingua franca" to do with the human (and planetary) condition and how it can be transformed." Similarly, the historian of religion Olav Hammer termed it "a common denominator for a variety of quite divergent contemporary popular practices and beliefs" that have emerged since the late 1970s and are "largely united by historical links, a shared discourse and an "air de famille"". According to Hammer, this New Age was a "fluid and fuzzy cultic milieu". The sociologist of religion Michael York described the New Age as "an umbrella term that includes a great variety of groups and identities" that are united by their "expectation of a major and universal change being primarily founded on the individual and collective development of human potential."