Deepak Chopra is "very wealthy". He told me so himself, leaping to his feet to defend his personal brand of spirituality, and pacing up and down in front of me. "Spiritual people should not be ashamed of being wealthy," he declared. I did not disagree.

All this took place at Toward a Science of Consciousness, a biennial conference in Tucson, Arizona, where I was invited, along with Menas Kafatos and Leonard Mlodinow, to debate with the spiritual guru and purveyor of Ayurvedic medicine.

Chopra is used to debating with scientists, indeed his book with Mlodinow, War of the Worldviews, inspired the title of our debate. These science v spirituality debates can be rather frustrating because Chopra uses lots of scientific ideas in his books and talks – from quantum mechanics to evolution – but he tends to twist them just at the crucial point. For example, he claims that consciousness not only gave rise to the entire universe but also directs evolution. This means we are all evolving towards a higher state of consciousness. Nice thought – popular thought too – but it kind of misses the whole point that evolution by natural selection (and related processes) is a marvellously mindless process that does not require a designer or the power of consciousness to produce its wonders.

But my arguments took a different tack. I chose to tackle his brand of "spirituality" rather than his wobbly science, although I think he treats both in the same disingenuous way. He takes their underlying, and often uncomfortable, insights and then twists them into something far more palatable – into something everybody would like to be true.

The problem, as far as consciousness is concerned, is the same for both science and spirituality – it's dualism. We seem to be conscious selves having a stream of mental experiences in a physical world, yet there cannot be two kinds of stuff – the physical and the mental. Scientists tend to make matter primary and cannot explain how a physical brain creates subjective experiences; Chopra's version of spirituality makes consciousness primary but cannot explain how consciousness creates matter. Meanwhile mystics and meditators throughout the ages have said all this is illusion – ultimately "I" am not separate from the world around me. Seeing the true nature, or becoming enlightened, means seeing through the illusion to oneness, or realising non-duality.

I have been training in Zen for 30 years as well as being involved in consciousness research. So I am familiar with both sides. That's why I agreed with Chopra when, in his "workshop" the night before (actually a solid, three-hour lecture), he said: "There is no separation between mind and body … Self and other co-arise and fall away all the time."

"I am not a dualist," he proclaims. But he is. "How do you wiggle your toes?" he asks. "Isn't your mind sending an order to your feet?" or, "Before a brain can register a thought, a mind must think it … every step of the way is mind over matter … We override our brains all the time."

Aha – so there's a "me" that overrides "my brain". This is straight dualism and is precisely what most spiritual traditions deny. Their teachers know that denying the persistence and importance of our very own self is painful, as the Buddha did. They know it is hard to accept our self as an ephemeral construction (to put it in scientific terms), or something that arises and falls away all the time (in spiritual terms).

So Chopra twists his "spirituality" right back on itself into the old, familiar and comfortable idea that "I" exist, "I" control my own body, "I" am important and may even live forever. In his book Reinventing the Body, Resurrecting the Soul he gives "the soul the attention it deserves": a dualist project if ever there was one.

I'll give two further examples. In Ageless Body, Timeless Mind (two million copies sold) Chopra describes those timeless experiences familiar to long-term meditators and those who have spontaneous or drug-induced mystical experiences. The world does not disappear, yet self, time and space cease to have any meaning. All is one and time is gone. Whether you come at this from a scientific or spiritual perspective this makes sense as a process of dropping the usual illusions of self and separation.

Yet for Chopra this is "the quantum alternative to growing old". Through developing the timeless mind "the effects of ageing are largely preventable", he says. So he has slithered from what I think is a genuine insight about the nature of self and time to claiming to prevent ageing. Indeed, he claims that "in moments of transcendence, when time stands still, your biological clock will stop. The spirit is that domain of our awareness where there is no time."

The biological clock will stop? All those multiply-interlinked chemical and biochemical processes that provide aspects of timing in a complex body will stop? I doubt it. His evidence includes the effect of meditation on the enzyme telomerase, which he interprets as proof that consciousness has the power to slow ageing. I interpret it as that meditation, with all its effects on attention, relaxation and attitude, has positive health benefits too.

Finally there is that question of wealth itself. I ended my presentation on his mega-bestseller The Seven Spiritual Laws of Success, where Chopra considers "the creation of wealth". One might be forgiven for thinking he is talking about "spiritual wealth"; about the joy, equanimity, compassion or peace that may result from spiritual practice. But no. He is urging us to align our consciousness "with the subtle yet powerful, unseen forces that affect the flow of money in our lives".

What then of enlightenment? Aside from his video game promising "a soothing journey to enlightenment", in his lecture Chopra described enlightenment as "getting rid of the person that never was". I agree with him (again). This is the whole thrust of the spiritual journey, that you discover that you aren't, and never were, who you thought you were. The feeling of being a powerful entity who persists through time and who will either die or live on when your body dies is an illusion. Yet it is surely precisely this illusory self who craves an "ageless body" and an eternal soul, and who longs for success, material wealth and "control over the flow of money".

One who has transcended the ordinary illusions of self and duality might or might not be wealthy, but they would surely not crave power and money or encourage others to do so. This is why I concluded by saying: "Deepak, you may be happy to call this 'spirituality' but I am not." And this, in turn, is why he leapt so eagerly to his feet to defend himself and his enormous wealth.

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