Objectivism is the system Ayn Rand built in the mid-twentieth century, combining metaphysical realism, a foundationalist epistemology, ethical egoism and an absolute defense of laissez-faire capitalism into a deliberately closed and comprehensive worldview.
Its structure runs from metaphysics to politics in a single chain. Reality exists independently of consciousness. Reason is the only means of knowing it. Each person's own life is the standard of value, from which Rand derives rational self-interest as a virtue and altruism as a genuine vice, not an excess. Individual rights follow as the social application of that ethics, and capitalism follows as the only system that respects them, defended on moral grounds and not on efficiency. Rand made the case first through fiction, in The Fountainhead (1943) and Atlas Shrugged (1957), and only afterward in essays such as The Virtue of Selfishness (1964).
Academic philosophy has largely dismissed the system. The objections are that the derivation of egoism from the requirements of survival does not go through, and that Rand engaged with the philosophical tradition mostly to denounce it. Objectivism's own institutional history has been unusually schismatic: the break with Nathaniel Branden in 1968, and the later split between the Ayn Rand Institute and the more latitudinarian Atlas Society, both turned on who was entitled to interpret the system.
Its influence on American political argument is out of all proportion to its academic standing. It runs through the libertarian movement, which Rand herself despised, regarding libertarians as plagiarists who had taken her politics while discarding its philosophical foundation, and through readers who met the novels early and the objections late. It remains among the few philosophical systems most of whose adherents arrived through fiction.