Imagine that somehow your body and brain were separated but still working as a team. Your brain sits in a vat. Your body can move around, remotely connected to your brain by some kind of signal.

So where are you? In the vat or with your body? Or both places at once?

Such were the questions raised by Dr. Daniel C. Dennett, a prolific and often provocative American philosopher whose theories – including the essence of consciousness itself – reached wide audiences as one of the most discussed thinkers on the human experience.

In the broadest terms, Dennett used science to challenge notions of faith and inherited traditions such as ideas of a higher mind and immutable soul. “There’s simply no polite way to tell people they’ve dedicated their lives to an illusion,” said Dennett, who died Friday at a hospital in Portland at age 82.

To him, human brains are essentially biochemical supercomputers, triggering decisions and actions. Concepts such as free will are layered on to help make sense of existence and guide laws and communities, he asserted.

Even self-awareness – what makes you “you” – is another byproduct of our neurons, he theorized. The building blocks of consciousness, memory and sense of self, are no different from other brain functions, he said, and should be studied the same way by neuroscientists and others.

“The only meaning of life worth caring about,” he once said, “is one that can withstand our best efforts to examine it.” This became one of the pillars in a field known as cognitive science, led by Dennett at Tufts University since the 1970s and explored in his more than 20 books and hundreds of essays, often written in an engaging and intentionally flippant style meant to introduce his ideas to general audiences.

His lectures were often sold-out affairs. Consciousness and subjective perceptions – what is called “qualia,” the awe of a sunrise or the green of greenness – is simply the brain at work, he told audiences. To believe otherwise is “profoundly naive and anti-scientific,” he said in a 2013 interview.

“I’m a robot, and you’re a robot, but that doesn’t make us any less dignified or wonderful or lovable or responsible for our actions,” he said. “Why does our dignity depend on our being scientifically inexplicable?’’

His ideas began to take shape one day in 1976 while driving on the Massachusetts Turnpike, he wrote in his 2023 memoir, “I’ve Been Thinking.” He wondered what would happen if his brain was successfully transplanted to his chest. Would he still think that his brain was in its old spot, right behind his eyes?

That led to “Where Am I?” his seminal essay that included the brain in the vat. In an odd but entertaining yarn, Dennett built a story about being separated from his brain and later receiving a new body after his original body was damaged beyond repair. His scenario: his “Dennettness” was transferrable; consciousness could be stored in the same way as a computer backup.

The essay, as much science fiction as philosophy, cast uncertainty over long-held beliefs on the dominance of mind over body.

There was no shortage of criticism of Dennett’s outlook. Many theologians and faith leaders saw his views as hollow and bleak. (The writer Christopher Hitchens called Dennett part of his “four horsemen of new atheism,” along with evolutionary biologist Richard Dawkins and neuroscientist Sam Harris.) Ethicists and others derided Dennett’s work as too narrow, leaving no room to explain the complexity of human emotions such as empathy and compassion.

Dennett never shied from intellectual sparring – and could become combative when pushed hard.

He engaged in a bitter duel with renowned evolutionary scientist Stephen Jay Gould, who objected to Dennett’s assertion that evolution was determined by natural selection alone. Gould’s work gave significant weight to other evolutionary factors such as genetic mutations and cataclysmic events. From then on, Dennett dubbed any opposition to his views on evolution as “goulding.” (He coined a word for himself: a “dennett” was “an artificial enzyme used to curdle the milk of human intentionality.”)

In “Darwin’s Dangerous Idea” (1995), one of Dennett’s most-read works, he argued that natural selection led to the size and capacities of the human brain, which, in turn, allowed for language, scientific inquiry and discoveries – in addition to wars and other self-imposed miseries.

“I think the people who don’t like magic tricks explained to them are also the people who don’t like free will explained to them, or consciousness,” he told the Guardian. “‘How rude! How philistine, to explain, to even try! How dare you!’”

He put his atheism to the test against clerics and others, including a debate with Christian philosopher Alvin Plantinga that was published as the book “Science and Religion: Are They Compatible?” (2010).

Once, in a radio interview, a pastor told Dennett that faith was stronger than reason. “Right there, I submit, lies one of the greatest dangers to civilization,” Dennett recounted in his memoir, “As I have said, religious faith gives people a gold-plated excuse to stop thinking.”

A 2013 book with colleague Linda LaScola, “Caught in the Pulpit: Leaving Belief Behind,” included interviews with clerics of various denominations who acknowledged they were secret atheists but said religion provided comfort to their congregations. The book became a play, “The Unbelieving,” by Marin Gazzaniga that was staged in New York in 2022.

On free will, Dennett tangled with deep-rooted traditions on principles that a higher mind guided principles such as morality and social responsibility. He said the physical brain was really in the driver’s seat and that scientists, not sociologists or theologians, had the answers. Yet he called the idea of free will a necessary “illusion” to underpin a functioning society.

“Our system of law and order, of punishment, and praise and blame, promise keeping, promise making, the law of contracts, criminal law – all of this depends on one notion or another of free will,” he wrote in “Intuition Pumps and Other Tools for Thinking” (2013). In reality, he asserted, “our systems of law are built on foundations of sand.”

BOSTON ROOTS

Daniel Clement Dennett III was born on March 28, 1942, in Boston. He spent part of his childhood in Beirut, where his father was a covert intelligence agent, code-named “Carat,” while assigned to the U.S. Embassy as cultural attaché. His mother, a teacher, was an English instructor at the American Community School.

His father, who had a doctorate in Islamic Studies from Harvard University, was killed in a plane crash in Ethiopia in 1947. The family returned to the United States shortly after.

He graduated with a bachelor’s degree in philosophy from Harvard in 1963, and earned his doctorate in philosophy in 1965 from the University of Oxford, where he studied under Gilbert Ryle, whose work opposed the distinction French philosopher René Descartes (“I think, therefore I am”) made between body and mind.

Dennett recalled one night at Oxford when he asked his landlord’s son, a medical student, the question: What is the brain made of? “He drew me a simple picture of a neuron,” he said, “and pretty soon I was off to the races.’’

Dennett taught at the University of California at Irvine from 1965 to 1971, then moved to Tufts outside Boston, his academic base for the rest of his entire career, serving as director of the university’s Center for Cognitive Studies and, in recent years, as a professor emeritus.

Some of his brief stints away from Tufts included working with a team at the Massachusetts Institute of Technology in 1993 seeking to create a humanoid robot called Cog. (Dennett believed one of the greatest dangers of artificial intelligence is possibly destroying the “links of trust that have made civilization possible.”)

Among Dennett’s books were “Brainstorms: Philosophical Essays on Mind and Psychology” (1978); “Consciousness Explained” (1991), and “Kinds of Minds: Toward an Understanding of Consciousness” (1996).

A veteran sailor, he named his 42-foot sailboat Xanthippe after Socrates’ wife. Sailing the New England coast, he said, was a welcomed stretch of physical immediacy, such as setting the sails and studying the wind, compared with the intellectual rigors of philosophy.

“If you had to try to understand everything going on your brain,” he said at a Tufts lecture, “you wouldn’t have time to do anything else.”

Dennett died of complication from lung disease, said his wife, Susan Bell Dennett. Other survivors include two children; two sisters; and six grandchildren. He lived in Cape Elizabeth.

In his book “Breaking the Spell,” Dennett wrote – in clear self-reference – of the powerful combination of a philosopher who embraced science.

“You will find worlds within worlds, beauties you could not heretofore imagine,” he wrote, “and your own mundane preoccupations will shrink to proper size, not all that important in the greater scheme of things.”