His work touches on a range of topics, including rationality, religion, ethics, free will, neuroscience, meditation, psychedelics, philosophy of mind, politics, terrorism, and artificial intelligence.

[2][3][4] Harris's first book, The End of Faith (2004), won the PEN/Martha Albrand Award for First Nonfiction and remained on The New York Times Best Seller list for 33 weeks.

[7] Harris has debated with many prominent figures on the topics of God or religion, including William Lane Craig, Jordan Peterson, Rick Warren, Robert Wright, Andrew Sullivan, Cenk Uygur, Reza Aslan, David Wolpe, Deepak Chopra, Ben Shapiro, and Peter Singer.

[21] Leaving Stanford in his second year, a quarter after his psychoactive experience, he visited India and Nepal, where he studied meditation with teachers of Buddhist and Hindu religions,[21][22] including Dilgo Khyentse.

[22] He received a Ph.D. in cognitive neuroscience in 2009 from the University of California, Los Angeles,[22][26][27] using functional magnetic resonance imaging to conduct research into the neural basis of belief, disbelief, and uncertainty.

He came to prominence for his criticism of religion (Islam in particular) and he is described as one of the Four Horsemen of Atheism, along with Richard Dawkins, Christopher Hitchens, and Daniel Dennett.

[33] The podcast focuses on a wide array of topics related to science and spirituality, including philosophy, religion, morality, free will, neuroscience, meditation, psychedelics and artificial intelligence.

[14] Often invoking the non-violent nature of Jainism[39] to contrast with Islam,[40] Harris argues that the differences in religious doctrines and scriptures are the main indicators of a religion's value.

[48] In June and July 2018, he met with Canadian psychologist Jordan Peterson for a series of debates on religion, particularly the relationship between religious values and scientific fact in defining truth.

[56] He is also critical of liberal Christianity – as represented, for instance, by the theology of Paul Tillich – which he argues claims to base its beliefs on the Bible despite actually being influenced by secular modernity.

Compassion, awe, devotion, and feelings of oneness are surely among the most valuable experiences a person can have",[21] saying:[SH 5] Everything of value that people get from religion can be had more honestly, without presuming anything on insufficient evidence.

[58] In Waking Up: A Guide to Spirituality Without Religion (2014), Harris describes his experience with Dzogchen, a Tibetan Buddhist meditation practice, and recommends it to his readers.

[57] He writes that the purpose of spirituality (as he defines it – he concedes that the term's uses are diverse and sometimes indefensible) is to become aware that our sense of self is illusory, and says this realization brings both happiness and insight into the nature of consciousness, mirroring core Buddhist beliefs.

[57][14] When you learn how to meditate, you recognize that there is another possibility, which is to be vividly aware of your experience in each moment in a way that frees you from routine misery.Harris considers that the well-being of conscious creatures forms the basis of morality.

Dennett said the book was valuable because it expressed the views of many eminent scientists, but that it nonetheless contained a "veritable museum of mistakes" and that "Harris and others need to do their homework if they want to engage with the best thought on the topic.

[79] Just a few days before the elections, he joined in a debate on the Honestly podcast where he argued in favor of supporting Kamala Harris, while Ben Shapiro presented the case for Donald Trump.

[87] New York Times book reviewer Bari Weiss described the group as "a collection of iconoclastic thinkers, academic renegades and media personalities who are having a rolling conversation – on podcasts, YouTube and Twitter, and in sold-out auditoriums – that sound unlike anything else happening, at least publicly, in the culture right now.

[88] In 2023 during an interview with The Daily Beast, Harris explained that he had broken away from the intellectual dark web due to disagreements with Bret Weinstein, and Maajid Nawaz's "obsession" with COVID-19 conspiracy theories and criticism of COVID-19 policies.

[89] In April 2017, Harris hosted the social scientist Charles Murray on his podcast, discussing topics including the heritability of IQ and race and intelligence.

[SH 16] Harris stated the invitation was out of indignation at a violent protest against Murray at Middlebury College the month before and not out of particular interest in the material at hand.

[91] In the Vox article, scientists, including Eric Turkheimer, Kathryn Paige Harden, and Richard E. Nisbett, accused Harris of participating in "pseudoscientific racialist speculation" and peddling "junk science".

[97] In a 2016 interview with Al Jazeera English's UpFront, Chomsky further criticized Harris, saying he "specializes in hysterical, slanderous charges against people he doesn't like.

"[96] Other writers and political commentators including Glenn Greenwald,[98] Reza Aslan,[99] and Chris Hedges have also accused Harris of Islamophobia and or bigotry.

Affleck also compared Harris's and Maher's rhetoric to that of people who use antisemitic canards or define African Americans in terms of intraracial crime.

"[112] Hatewatch staff at the Southern Poverty Law Center (SPLC) wrote that members of the "skeptics" movement, of which Harris is "one of the most public faces", help to "channel people into the alt-right.

[119][120][121][122] In his review of The End of Faith, American historian Alexander Saxton criticized what he called Harris's "vitriolic and selective polemic against Islam", (emphasis in original) which he said "obscure[s] the obvious reality that the invasion of Iraq and the War against Terror are driven by religious irrationalities, cultivated and conceded to, at high policy levels in the U.S., and which are at least comparable to the irrationality of Islamic crusaders and Jihadists.

[130] Additionally, Free Will received a mixed academic review from philosopher Paul Pardi, who said that while it suffers from some conceptual confusions and that the core argument is a bit too "breezy", it serves as a "good primer on key ideas in physicalist theories of freedom and the will".

[134][58] It was praised by Frank Bruni, for example, who described it as "so entirely of this moment, so keenly in touch with the growing number of Americans who are willing to say that they do not find the succor they crave, or a truth that makes sense to them, in organized religion.

"[132] In 2018, Robert Wright, a visiting professor of science and religion at Union Theological Seminary, published an article in Wired criticizing Harris, whom he described as "annoying" and "deluded".

Wright wrote that Harris, despite claiming to be a champion of rationality, ignored his own cognitive biases and engaged in faulty and inconsistent arguments in his book The End of Faith.