Lewis was born in Llandudno, Wales, and educated at Caernarfon grammar school, the University College of North Wales, Bangor (graduating with a first-class degree in philosophy in 1932), and Jesus College, Oxford (graduating with a BLitt in 1935).
He was then a lecturer in philosophy at Bangor, becoming professor in 1947. In 1955, he was appointed Professor of the History and Philosophy of Religion at the University of London, retiring in 1977. His works included Morals and the New Theology (1947), Morals and Revelation (1951), Our Experience of God (1959), The Elusive Mind (1969), The Self and Immortality (1973), Persons and Life after Death (1978) and The Elusive Self (1982). He also published in Welsh. His interest in comparative religion led to his becoming founding editor of the journal Religious Studies, holding the post from 1964 to 1979. He edited the Muirhead Library of Philosophy from 1947 to 1978. He also served as president of the Aristotelian Society from 1962 to 1963, and as chairman of the council of the Royal Institute of Philosophy from 1965 to 1968.
Lewis wrote there is no incoherence in the notion of personal survival in his book The Self and Immortality (1973). Michael Marsh in a review wrote the book offered a "substantial defense" for interactionist dualism. In his book Persons and Life after Death (1978) Lewis argued that the ultimate basis for a belief in life after death is from religion. He claimed this belief could mean for some, the resurrection of the body, survival in an astral body or survival in a disembodied form. Lewis wrote that disembodied survival is most plausible from a religious point of view.
Lewis was a Christian who sought common ground between the world's religions and argued there is a sense of transcendental reality in all of them. However, he argued against Buddhist and monistic views in which the self is considered to be an illusion.
In his book The Elusive Self (1982) Lewis argued that mental states are "distinct in nature from physical states but constantly interacting with them" and there is a "subject, or a self or soul, which remains constant and is uniquely involved in all the flow of our mental states or experiences." The philosopher Gareth Matthews gave the book a negative review claiming Lewis had offered no evidence for dualism. On the subject of dreamless sleep, Lewis wrote the self ceases to be. According to Matthews the belief that the self can pop in and out of existence would be alarming to some readers but Lewis had no problem with accepting this view. Matthews concluded that Lewis's controversial claims were deliberately left with no direct argumentative support. Eugene Long gave the book a positive review stating Lewis had given an adequate defence for the dualistic position and the existence of the self. Long has written that Lewis was a philosophical realist, similar to John Baillie and John Cook Wilson.
- Morals and the New Theology (1947)
- Morals and Revelation (1951)
- Gwybod am Dduw [Our Knowledge of God] (1952)
- Our Experience of God (1959)
- Freedom and History (1962)
- Clarity is Not Enough (1963)
- World Religions: Meeting Points and Major Issues [with Robert Lawson Slater] (1966)
- Dreaming and Experience (1968)
- The Elusive Mind (1969)
- Philosophy of Religion (1969)
- The Self and Immortality (1973)
- Persons and Life after Death (1978)
- Persons and Survival: Essays by Hywel D. Lewis and Some of His Critics (1978)
- Logic, Ontology, and Action (1979)
- Pwy yw Iesu Grist? [Who is Jesus Christ?] (1979)
- Jesus in the Faith of Christians (1981)
- The Elusive Self (1982)
- Freedom and Alienation (1985)
- Sutherland, Stewart. (1993). Obituary: Hywel David Lewis 1910–1992. Philosophy. Vol. 68, No. 264. pp. 263–264.
- Brown, Stuart; Collinson, Diane; Wilkinson, Robert. (1996). Biographical Dictionary of Twentieth-Century Philosophers. Routledge. ISBN 0-415-06043-5 "Lewis is best known for his defense of a dualist view of mind and body in opposition to the more prevalent behaviorist views advocated by Ryle and others. He defended with some success a belief in personal survival against the belief common amongst analytical philosophers that immortality was inconceivable. He acquired a high international reputation, particularly in India and America, where he received and took many invitations to lecture and accept other honors."
- Helm, Paul (2004). "Lewis, Hywel David (1910–1992)". Oxford Dictionary of National Biography. Oxford University Press. Retrieved 5 October 2008. CS1 maint: discouraged parameter (link)
- Sutherland, Stewart. (1976). The Self and Immortality. by H. D. Lewis. Mind. New Series, Vol. 85, No. 337. pp. 141–143.
- Marsh, Michael. (1977). Beyond Death: The Rebirth of Immortality. The Hastings Center Report. Vol. 7, No. 5. pp. 40–42.
- Daher, Adel. (1981). Persons and Life after Death by Hywel D. Lewis. The Journal of Religion. Vol. 61, No. 1. pp. 106–107.
- Brown, Stuart; Bredin, Hugh. (2005). The Dictionary of Twentieth-Century British Philosophers: 2 Volumes. Thoemmes. p. 566. ISBN 1-84371-096-X
- Matthews, Gareth. (1985). The Elusive Self by Hywel D. Lewis; Selfless Persons by Steven Collins. Philosophy and Phenomenological Research. Vol. 45, No. 3. pp. 461–465.
- Long, Eugene. (1985). The Elusive Self by H. D. Lewis. The Review of Metaphysics. Vol. 38, No. 3. pp. 655–657.
- Long, Eugene. (2003). Twentieth-Century Western Philosophy of Religion 1900–2000. Kluwer Academic Publishers. p. 128. ISBN 0-7923-6285-3
- Russell Aldwinckle. (1979). Persons and Life after Death by Hywel D. Lewis. Religious Studies. Vol. 15, No. 1. pp. 122–124.
- Scott Dunbar. (1980). The Concept of Self: Some Reflections on H. D. Lewis' "The Self and Immortality". Religious Studies. Vol. 16, No. 1. pp. 37–48.
- David Cairns. (1982). Jesus in the Faith of Christians by Hywel D. Lewis. Religious Studies. Vol. 18, No. 1. pp. 102–105.
- Galen Johnson. (1984). The Elusive Self by Hywel D. Lewis. International Journal for Philosophy of Religion. Vol. 15, No. 1/2. pp. 102–103.
- John Knox. (1974). The Self and Immortality. Religious Studies. Vol. 10, No. 1. pp. 89–100.
- Hywel Lewis, Charles Whiteley. (1955). The Cognitive Factor in Religious Experience. Proceedings of the Aristotelian Society, Supplementary Volumes. Vol. 29, Problems in Psychotherapy and Jurisprudence. pp. 59–92.
- Hywel Lewis, Antony Flew. (1975). Survival. Proceedings of the Aristotelian Society, Supplementary Volumes Vol. 49. pp. 211–247.
- Eric Matthews. (1984). The Elusive Self by Hywel D. Lewis. Mind. New Series, Vol. 93, No. 369. pp. 152–154.
- Louis Pojman. (1981). Persons and Life after Death by H. D. Lewis. International Journal for Philosophy of Religion. Vol. 12, No. 3. pp. 189–191.
- H. H. Price. (1974). The Self and Immortality by H. D. Lewis. Philosophy. Vol. 49, No. 187. pp. 102–106.
- Stewart Sutherland. (1989). Religion, Reason and the Self: Essays in Honour of Hywel D. Lewis. University of Wales Press.