Smith was born in Toronto, Canada, the son of Victor Arnold Smith and Sarah Cory Cantwell. He was the younger brother of Arnold Smith. Smith received his B.A. with honours in Oriental Languages in 1938 from the University of Toronto. After having his thesis rejected at the University of Cambridge for its Marxist critique of the British Raj, he and his wife Muriel Mackenzie Struthers spent seven years in India (1940-1946). During this time Smith taught Indian and Islamic history at the Forman Christian College in Lahore. In 1948 he obtained his Ph.D in Oriental Languages at Princeton University, after which he taught at McGill, founding the McGill University Institute of Islamic Studies in 1952. From 1964 to 1973 Smith taught at the Harvard Divinity School. He left Harvard for Dalhousie University in Halifax, NS, where he founded their Department of Religion. In 1978 he returned to Harvard, and remained there for the duration of his career.
In his most controversial work, The Meaning and End of Religion, Smith contends that religion as now understood, rather than being a universally valid category as is generally supposed, is a peculiarly European construct of comparatively recent origin. He sets out, chapter by chapter, to demonstrate that none of the so-called founders of the world's major religions had any such intention: not one of them, in other words, set out to initiate what the world sees today. The one exception on the face of it, Smith concedes, is Islam. In a chapter titled The special case of Islam, Smith - himself an Presbyterian and ordained minister in the United Church of Canada whose academic speciality was Islam - argues that The Prophet would have been, above all others perhaps, deeply alarmed at any suggestion that he was starting a new religion. Indeed, Smith points out, Arabic, strictly speaking, doesn't even have a word for religion in the European sense: the word din, customarily translated as such, significantly differs in a number of important respects.
Smith suggests that practitioners of any given faith do not, historically, come to regard what they do as 'religion' until they have collectively sprouted that form of self-regard by which they absorb, so to speak, the perspective of the outsider, to see what they do as in some way different. Religion in the contemporary sense of the word is for Smith the product, in a sense, of both identity politics and apologetics :
"One's own 'religion' may be piety and faith, obedience, worship, and a vision of God. An alien 'religion' is a system of beliefs or rituals, an abstract and impersonal pattern of observables. A dialectic ensues, however. If one's own 'religion' is attacked, by unbelievers who necessarily conceptualize it schematically, or all religion is, by the indifferent, one tends to leap to the defence of what is attacked, so that presently participants of a faith - especially those most involved in argument - are using the term in the same externalist and theoretical sense as their opponents. Religion as a systematic entity, as it emerged in the seventeenth and eighteenth centuries, is a concept of polemics and apologetics" (p. 43).
Through an etymological study of 'religion' (religio, in Latin), Smith further contends that the term, which at first, and for most of the centuries, denoted an attitude towards a relationship between God and 'man' (p. 26), has, through conceptual slippage, come to mean a "system of observances or beliefs" (p. 29), a historical tradition which has been institutionalized through a process of reification. Whereas 'religio' denoted personal piety, 'religion' refers to an abstract entity (or transcendental signifier) which Smith claims does not exist.
Smith argues that the term as found in Lucretius and Cicero was internalized by the Catholic church through Lactantius and Augustine. During the Middle Ages it was superseded by the term "faith", which Smith favors by contrast. In the Renaissance, via the Christian Platonist Marsilio Ficino, 'religio' becomes popular again, retaining its original emphasis on personal practice even in John Calvin's Christianae Religionis Institutio (1536). During seventeenth century debates between Catholics and Protestants, religion begins to refer to an abstract system of beliefs, especially when describing an oppositional structure. Through the Enlightenment this concept is further reified, so that by the nineteenth century Hegel defines religion as 'Begriff', "a self-subsisting transcendent idea that unfolds itself in dynamic expression in the course of ever-changing history ... something real in itself, a great entity with which man has to reckon, a something that precedes all its historical manifestation" (p. 47).
Smith concludes his exercise in etymology by arguing that religion now has four meanings: 1) personal piety; 2&3) "an overt system of beliefs, practices, values" related to the time and place of community religion. The term is split into two meanings, a. the 'ideal' religion of the theologian, and b. the 'empirical phenomenon' of the lived tradition; and 4) a generic summation, or universal category, ie: religion in general (p. 48-9).
The Meaning and End of Religion remains Smith's most influential work. The writer who, in turn, has taken up and applied most vigorously Smith's emphases is the former nun Karen Armstrong.