Born in Cambridge, England but of Scottish parents, Smart began his education locally, attending The Leys School, a boarding school in the area. His younger brothers also became professors: Alastair (1922-1992) was Professor of Art History at Nottingham University; Ninian was a professor of Religious Studies and a pioneer in that field. Their father, William Marshall Smart, was John Couch Adams Astronomer at Cambridge University and later Regius Professor of Astronomy at Glasgow. In 1950, W. M. Smart was President of the Royal Astronomical Society. In 1946, Jack Smart graduated from the University of Glasgow with an M.A., followed by a B.Phil. from Oxford University in 1948. He then worked as a Junior Research Fellow at Corpus Christi College, Oxford for two years.

He arrived in Australia in August 1950 to take up the Chair of Philosophy at the University of Adelaide, which he occupied from 1950 until 1972. After twenty-two years in Adelaide, he moved to La Trobe University where he was Reader in Philosophy from 1972-76. He then moved to the Australian National University where he was Professor of Philosophy in the Research School of Social Sciences from 1976 until his retirement in 1985, and where the annual Jack Smart Lecture is held in his honor. He is currently Emeritus Professor at Monash University.

At first Smart was a behaviourist before becoming an early proponent of Type Identity Theory. The Identity Theory of Mind (Stanford Encyclopedia of Philosophy)

Smart's main contribution to metaphysics is in the area of philosophy of time. He has been an influential defender of the B-Theory of time, and of perdurantism.

His most important original arguments in this area concern the passage of time, which he claims is an illusion. He argues that if time really passed, then it would make sense to ask at what rate it passes, but this requires some second time-dimension with respect to which passage of normal time can be measured. This in turn faces the same problems, and so there must be a third time-dimension, and so on. This is called the rate of passage argument.

Smart has changed his mind about the nature and causes of the illusion of the passage of time. In the 1950s, he held that it was due to people's use of anthropocentric temporal language. He later came to abandon this linguistic explanation of the illusion in favour of a psychological explanation in terms of the passage of memories from short-term to long-term memory.

In the philosophy of mind, Smart is a physicalist. In the 1950s, he was one of the originators, with Ullin Place, of the Mind-Brain Identity Theory, which claims that particular states of the mind are identical with particular states of the brain. This view was dubbed "Australian materialism" by its detractors, in reference to the stereotype of Australians as down-to-earth and unsophisticated.

Smart's identity theory dealt with some extremely long-standing objections to physicalism by comparing the mind-brain identity thesis to other identity theses well-known from science, such as the thesis that lightning is an electrical discharge, or that the morning star is the evening star. Although these identity theses give rise to puzzles such as Gottlob Frege's puzzle of the Morning Star and Evening Star, in the scientific cases it would be absurd to reject the identity theses on this ground. Since the puzzles facing physicalism are strictly analogous to the scientific identity theses, it would also be absurd to reject physicalism on the grounds that it gives rise to these puzzles.

In ethics, Smart is a defender of utilitarianism. Specifically, he defends "extreme", or act utilitarianism, as opposed to "restricted", or rule utilitarianism. The distinction between these two types of ethical theory is explained in his essay Extreme and Restricted Utilitarianism.

Smart gives two arguments against rule utilitarianism. According to the first, rule utilitarianism collapses into act utilitarianism because there is no adequate criterion on what can count as a "rule". According to the second, even if there were such a criterion, the rule utilitarian would be committed to the untenable position of preferring to follow a rule, even if it would be better if the rule were broken, which Smart calls "superstitious rule worship".

Another aspect of Smart's ethical theory is his acceptance of a preference theory of well-being, which contrasts with the hedonism associated with "classical" utilitarians such as Jeremy Bentham. Smart's combination of the preference theory with consequentialism is sometimes called "preference utilitarianism".

Smart's arguments against rule utilitarianism have been very influential, contributing to a steady decline in its popularity among ethicists during the late 20th century. Worldwide, his defence of act utilitarianism and preference theory has been less prominent but has influenced philosophers who have worked or been educated in Australia, such as Frank Jackson, Philip Pettit, and Peter Singer.

One of Smart's two entries in the Philosophical Lexicon refers to his approach to the consequences of act utilitarianism: to "outsmart" an opponent is "to embrace the conclusion of one's opponent's reductio ad absurdum argument." This move is more commonly called "biting the bullet".