[1] Kingsley's work argues that the writings of the presocratic philosophers Parmenides and Empedocles, usually seen as rational or scientific enterprises, were in fact expressions of a wider Greek mystical tradition that helped give rise to western philosophy and civilisation.
[7][8][9][10] Kingsley reads the poems of Parmenides and Empedocles as esoteric, initiatory texts designed to lead the reader to a direct experience of the oneness of reality and the realisation of his or her own divinity.
However, Kingsley agrees with other recent critics in contending that later ancient philosophers such as Plato, Aristotle, and Theophrastus, among others, misinterpreted and distorted their predecessors; hence, conventional scholarship that uncritically accepts their misrepresentations of the presocratics is necessarily flawed.
[11][12][13] Kingsley's procedure is to read presocratic texts in historical and geographical context, giving particular attention to the Southern Italian[14][15] and Sicilian[16][17] backgrounds of Parmenides and Empedocles.
[18] Kingsley presents Parmenides and Empedocles as representatives of a mystical tradition that helped give rise to western philosophy and civilisation and that is still available to people today.
[22] Similarly, Kingsley argues that the imagery and wording of the proem, or introductory part, of Parmenides' poem record an initiate's descent to the underworld and indicate a mystical background connected to the ancient practice of healing and meditation known as incubation.
That this is no mere material or metaphysical monism is indicated by the initiatory motifs of the proem; the setting and hymnal language of "Fragment Eight"; the unnamed goddess as the speaker of these words; and the figure of the historical Parmenides as priest of Apollo.
His words are esoteric seeds that must be planted in the earth of the body and tended with good will, purity, and attention—since they possess the power, if treated properly, to germinate and grow into divine awareness.
"[35] He named Kingsley's first two published books as prime examples of studies which "encourage us to expect that early Greek philosophy will be as effective at stimulating thought and reinterpretation in the next century as it has been during the past hundred years.
"[36] In 2013 Gabriele Cornelli, Professor of Ancient Philosophy at the University of Brasilia and Director of the Archai UNESCO Chair on the Origins of Western Thought, published his historical work In Search of Pythagoreanism.
[37] Cornelli credits Kingsley's careful attention to the language used by ancient Greek writers, coupled with his expertise in history, archaeology and the anthropology of religion, for allowing him to offer "unique and bold solutions" to the most sensitive issues.
Outside the well-defined area of presocratic philosophy, Kingsley's published books and articles have also become a fundamental point of reference for experts in the field of ancient Greek religion.
[43][44][45] In September 2021 contemporary philosopher and scholar of religions Samuel Loncar wrote an in-depth survey of Kingsley's work for Marginalia, a channel of the Los Angeles Review of Books.
Kingsley's influence on Islamic scholarship is visible in the published work of Seyyed Hossein Nasr, one of the most influential Muslim scholars in the world and also a practicing Sufi.
Nasr begins his seminal book Islamic Philosophy from its Origin to the Present[47] with a detailed analysis of “the recent brilliant studies of Peter Kingsley”[48] and, with their help, argues for the existence of a single prophetic tradition extending all the way from Parmenides and Empedocles through to Muhammad.
He has separately published extended reviews of some of Kingsley's books,[49] describing Reality as a work that “unveils a reality which, if understood and accepted, will transform the understanding of contemporary Western humanity of itself and of the roots of Western civilization…It deals with truths which are of the greatest existential importance, truths whose understanding is literally a matter of life and death.”[50] Additionally he contributed a foreword to the Persian translation of In the Dark Places of Wisdom, again pointing to the significance of Kingsley’s work not only for the theoretical study of Islam but also for practical Sufism.
[53] The film includes interviews with Huston Smith, Pir Zia Inayat Khan, Gregory Shaw and Cynthia Bourgeault about their individual perceptions and assessments of Peter Kingsley's work.
In his 2014 book American Gurus, Arthur Versluis, Professor of Religious Studies at Michigan State University and specialist in the history of western mysticism and esotericism, has devoted considerable space and effort to understanding the spiritual dimension of Kingsley's writings.
"[55] But whereas this phenomenon is typically associated with Indian or Tibetan traditions, through Kingsley's work we are faced with "direct, transformative illumination"[56] as an essential aspect of "the primordial wisdom of the West.
American non-dual spiritual teacher Adyashanti, who in 2020 invited Kingsley to appear on his Being Unlimited podcast, remarked that "Peter is someone who to me has…unparalleled knowledge and passion for the origins of western culture…He is an incredible scholar of that time period but he’s also a first-class mystic.
"[58] Joseph Rael, a Native American tribal elder, shaman, writer, and artist, penned the foreword to Kingsley's book A Story Waiting to Pierce You.