Leonard Peikoff was born in Winnipeg, Manitoba, Canada, to Samuel Peikoff, a surgeon, and his wife Bessie, a band leader. He attended the University of Manitoba from 1950 to 1953, then transferred to New York University, where he received his Bachelor of Arts and Master of Arts degrees in 1954 and 1957, respectively.

Peikoff received his Ph.D. in Philosophy from NYU in 1964, where his adviser was American Marxist and pragmatist philosopher Sidney Hook. His dissertation dealt with the metaphysical status of the law of non-contradiction in classical philosophy. He taught philosophy for many years at various colleges.

Peikoff first met Ayn Rand through his cousin Barbara Branden (then Barbara Weidman) in California when he was 17. He reports that this meeting with Rand made him aware of the profound importance of philosophy. When Rand later moved to New York, Peikoff decided to study philosophy at New York University. While studying at NYU from 1953 to 1964, he discussed philosophy with Rand in depth across a range of numerous philosophical issues. In biographical interviews with Rand recorded in the early 1960s, she stated that her discussions with Peikoff were part of her motive for completing her monograph on concept-formation, Introduction to Objectivist Epistemology.

Peikoff, along with Nathaniel Branden, Alan Greenspan, Barbara Branden and a number of other close associates, who jokingly called themselves "The Collective", met frequently with Rand to discuss philosophy and politics, as well as to read and discuss Rand's forthcoming novel, Atlas Shrugged, in her New York City apartment. In 1958 Branden founded the Nathaniel Branden Institute to promote Objectivism through lectures and educational seminars around the United States. Among its first lecturers were Peikoff and Greenspan. NBI became enormously successful, and soon had representatives all over the U.S. and around the world.

Following the dissolution of NBI in 1968, Peikoff continued to give private courses on a variety of topics to large Objectivist audiences. His lecture courses include: The Art of Thinking, Eight Great Plays, A Philosophy of Education, The History of Philosophy (in two "volumes" of lectures), Moral Virtue, Induction in Physics and Philosophy, An Introduction to Logic, Understanding Objectivism, and The Principles of Objective Communication. Rand endorsed his 1976 lecture series on Objectivism as the best exposition of her philosophy.

Rand made Peikoff the legal heir to her estate. As the executor of Rand's will, Peikoff handles the copyrights to all of her works (with the exception of Anthem, which has passed into the public domain). He can thus control their translation into other languages. He has the power of editing and releasing Rand's unpublished works, and has written forewords for all the current printings of her fiction.

Peikoff's first book, The Ominous Parallels (1982), was both an Objectivist explanation of the rise of the Third Reich and the Holocaust, and a warning that America was being led down the road to totalitarianism because of far-reaching intellectual parallels between Weimar Germany and the present-day United States.

In 1985, Peikoff founded the Ayn Rand Institute. Peikoff revised his 1976 lecture course on Objectivism (which Rand herself had endorsed as the best presentation of her philosophical system) into book form as The Philosophy of Ayn Rand, published in 1991, which Peikoff considers the first and only comprehensive presentation of Objectivism. In the mid-1990s, Peikoff taught courses at the Ayn Rand Institute's Objectivist Graduate Center (which was later reborn as the Objectivist Academic Center in 2000) along with Harry Binswanger and Peter Schwartz. From 1995 through 1999, Peikoff hosted a talk radio show focusing on philosophy and culture. In the '90s, Peikoff also elaborated on his theory of induction in the lecture series "Objectivism through Induction."

From February 2006 to June 2007 Peikoff posted an online Q and A of various questions relating to Objectivism that had been e-mailed to him, updating with a few more answers approximately every month. In August 2007 his website announced that this would be replaced with a podcast, which debuted on October 22 2007, and has been released irregularly on Mondays ever since.

, Peikoff is writing a book called The DIM Hypothesis, where he defines what he sees as the three approaches to integration in human thought—disintegration, integration, and misintegration—and applies the hypothesis to physics, philosophy, education, politics and other fields. He estimates that it "will be published in several years, probably in 2010."

Peikoff resides in Irvine, California, an affluent suburb in Orange County which is also home to the Ayn Rand Institute.

By his second wife, Cynthia, Peikoff has a daughter.

Split with Kelley

Peikoff views Objectivism as a "closed system" that consists solely of the philosophical principles Rand herself had articulated, and he considers disagreement with any of these principles a departure from Objectivism. The Ayn Rand Institute (ARI) promotes Peikoff's view of Objectivism.

The closed vs. open issue came to the fore when David Kelley, a philosopher then affiliated with Peikoff and ARI, published his essay "A Question of Sanction", arguing for greater open-mindedness in working with other groups. Kelley sees Objectivism as an "open system" that can evolve beyond Rand's own writings and beliefs. Peikoff presented his objections to Kelley in an article called "Fact and Value," arguing that Kelley's case contradicted Rand's understanding of the relationship between cognition and evaluation, facts and moral values. Peikoff concluded that Kelley was not a genuine Objectivist, and urged anyone agreeing with Kelley to leave the Objectivist movement. Ultimately, Kelley responded by founding the Institute for Objectivist Studies in 1990, which later changed its name to The Objectivist Center and finally The Atlas Society. (For more on the Peikoff-Kelley split, see Objectivist Movement#The Peikoff-Kelley split.)

Library of Congress dispute

Peikoff inherited many of Rand's manuscripts. During her lifetime, Rand had made a statement that she would bequeath her manuscripts to the Library of Congress. She later had reservations, and the bequest was not part of Rand's will. However, after her death, the Library of Congress requested the manuscripts. In July 1991, Peikoff had an assistant deliver the manuscripts of Rand's novels, except for the first and last pages of The Fountainhead, which he had framed. In their stead, he had the pages photocopied so that the manuscripts would be "complete."

On August 16, 1998, the Los Angeles Times published an article about Peikoff, including a comment he had made to the reporter about "stealing" the framed pages from the Library of Congress. The Library of Congress contacted Peikoff and demanded that he deliver the pages to them, deeming them to be U. S. government property. A complaint from the U.S. Department of Justice followed in October 2000, claiming over a million dollars in damages unless Peikoff turned over the pages. Peikoff consulted his lawyer, who advised him that the case could go either way if he went to court. Based on this advice, Peikoff released the pages to a representative of the Library of Congress.

Peikoff's political positions reflect those of Objectivism. He supports laissez-faire capitalism, arguing that the role of government in society should be limited to protecting individuals from the initiation of force and fraud. He opposes taxation, public education, welfare, business regulations, etc. He also opposes laws regulating pornography, euthanasia, stem cell research, etc. He is a supporter of abortion rights but criticizes defenders of abortion who label themselves "pro-choice", arguing that the term ignores the deeper philosophical issues involved. However, he carries on Rand's opposition to libertarianism in the 1960s, remaining sharply opposed to any description of Objectivist political philosophy as "libertarian" and to any collaboration with libertarian groups. He has been critical of American foreign policy, including both neoconservative and libertarian views as self-sacrificial. He objects to the terms "isolationist" or "interventionist" to describe his foreign policy views, stating that the only "intervention" the United States should enact is war and "only and when it is in self-defense."

Peikoff is known for campaigning on behalf of Elián González's right to remain in Florida, rather than returning to his father in Cuba, stating that "To send a child to rot in the prison of Cuba for the alleged sake of his own well-being is criminal hypocrisy. To send him there in order to preserve his father's rights is absurdity, since there are no parental or other rights in Cuba. To send him there because 'He needs a father, no matter what' is a mindless bromide. Does he need a father who has no choice but to watch his son being broken in mind and starved in body?"

Peikoff claims that Palestinian people prior to the establishment of the State of Israel consisted solely of "nomadic tribes meandering across the terrain," and that "the Arabs" today have no concept of property rights; indeed, that their "primitivist" antagonism to such rights is the root cause of Arab terrorism. He argues that Israel is a moral beacon which should not return any territory to Arabs or even negotiate with them. [1] Peikoff further argues that all Middle Eastern oil reserves are the rightful property of the West, "whose science, technology, and capital made its discovery and use possible." He advocates the outright destruction of "terrorist states," especially Iran, "as quickly as possible and with the fewest U.S. casualties, regardless of the countless innocents caught in the line of fire," not ruling out the use of nuclear weapons, arguing that moral responsibility for innocent deaths would lie with their governments rather than the United States. [2]

In 2004 Peikoff endorsed John Kerry (despite thinking of Kerry as a "disgustingly bad" candidate) against George W. Bush (whom he called "apocalyptically bad"), on the basis of Bush's religiosity and his refusal to crush Islamic regimes, especially Iran, along with his "doomed" economic policies. In advance of the 2006 elections, Peikoff recommended voting only for Democrats, to forestall what he sees is a rise in influence of the religious right, adding:

Given the choice between a rotten, enfeebled, despairing killer [Democrats], and a rotten, ever stronger, and ambitious killer [Republicans], it is immoral to vote for the latter, and equally immoral to refrain from voting at all because "both are bad."

In 2008, Peikoff refused to vote for either major party's ticket, saying that John McCain "comes across like a tired moron," calling Barack Obama a "lying phony" and Joseph Biden "a hilarious windbag," while saying of Sarah Palin that she is "an opportunist struggling to learn how to become a moron, a phony and a windbag."