The moment that the philosopher René Descartes first considered that famous phrase, "I think, therefore I am," he realized that the existence of his body could be doubted in a way that the existence of his mind could not. This led him to controversially believe that the mind must be made of different kind of stuff than the body; that the mind was, perhaps, immaterial.

Since then, centuries of science have cast a shadow over Descartes' argument. Physicists and biologists have been remarkably successful at explaining the workings of the universe and our bodies without having to appeal to anything more than what exists in the ontology of the material world.

But Descartes might be making a comeback, if a hunch by researcher Lucien Hardy at the Perimeter Institute in Canada has anything to say about it. Hardy has devised an experiment involving quantum entanglement that could finally prove whether the mind is truly material or immaterial, reports New Scientist.

How to measure something we don't quite understand

Quantum entanglement, something Albert Einstein called "spooky action at a distance," is a bizarre phenomenon that involves two particles that are mysteriously and instantaneously linked, such that action to one of the particles will immediately influence the other, even if they are light-years apart. Decades of quantum experiments have verified that entanglement is a real phenomenon, but we still don't understand how it works. You might say that entanglement is in the same camp with consciousness: it seems to exist even though we don't know how or why.

Now Hardy believes that the same experiments that prove that entanglement is a real phenomenon might be able to prove that human consciousness is immaterial. He has proposed a modified experiment involving two entangled particles are set 100 kilometers apart. At each end, around 100 humans are to be hooked up to EEG headsets that can read their brain activity. These EEG signals will then be used to influence the particles at each location.

Hardy contends that if the amount of correlation between the actions of the two entangled particles doesn’t match with previous experiments that study entanglement, it will imply a violation of quantum theory. In other words, such a result would suggest that the entangled measurements are being controlled by processes outside the purview of standard physics.

“[If] you only saw a violation of quantum theory when you had systems that might be regarded as conscious, humans or other animals, that would certainly be exciting. I can’t imagine a more striking experimental result in physics than that,” claimed Hardy. “We’d want to debate as to what that meant.”

There would certainly be a debate. Even if aberrant measurements did result from Hardy's new twist on an old quantum experiment, it's unclear whether this would mean that the mind is immaterial. But it's a result that would at least pour lots of new fuel on the ancient philosophical fire.

“There is an enormous probability that nothing special will happen, and that quantum physics will not change,” said Nicolas Gisin at the University of Geneva in Switzerland, who was not involved in Hardy's proposal. “But if someone does the experiment and gets a surprising result, the reward is enormous. It would be the first time we as scientists can put our hands on this mind-body or problem of consciousness.”